Electrode for electrolysis, laminate, wound body, electrolyzer, method for producing electrolyzer, method for renewing electrode, method for renewing laminate, and method for producing wound body

ABSTRACT

The present invention relates to an electrode for electrolysis, a laminate, a wound body, an electrolyzer, a method for producing an electrolyzer, a method for renewing an electrode, a method for renewing a laminate, and a method for producing a wound body. An electrode for electrolysis according to one aspect of the present invention has a mass per unit area of 48 mg/cm 2  or less and a force applied per unit mass·unit area of 0.08 N/mg·cm 2  or more.

TECHNICAL FIELD

The present invention relates to an electrode for electrolysis, alaminate, a wound body, an electrolyzer, a method for producing anelectrolyzer, a method for renewing an electrode, a method for renewinga laminate, and a method for producing a wound body.

BACKGROUND ART

For electrolysis of an alkali metal chloride aqueous solution such assalt solution and electrolysis of water, methods by use of anelectrolyzer including a membrane, more specifically an ion exchangemembrane or microporous membrane have been employed. This electrolyzerincludes many electrolytic cells connected in series therein, in manycases. A membrane is interposed between each of electrolytic cell toperform electrolysis. In an electrolytic cell, a cathode chamberincluding a cathode and an anode chamber including an anode are disposedback to back with a partition wall (back plate) interposed therebetweenor via pressing by means of press pressure, bolt tightening, or thelike.

The anode and the cathode for use in these electrolyzers now are eachfixed to the anode chamber or the cathode chamber of an electrolyticcell by a method such as welding and folding, and thereafter, stored ortransported to customers. Meanwhile, each membrane in a state of beingsingly wound around a vinyl chloride (VC) pipe is stored or transportedto customers. Each customer arranges the electrolytic cell on the frameof an electrolyzer and interposes the membrane between electrolyticcells to assemble the electrolyzer. In this manner, electrolytic cellsare produced, and an electrolyzer is assembled by each customer. PatentLiteratures 1 and 2 each disclose a structure formed by integrating amembrane and an electrode as a structure applicable to such anelectrolyzer.

CITATION LIST Patent Literature

-   Patent Literature 1

Japanese Patent Laid-Open No. 58-048686

-   Patent Literature 2

Japanese Patent Laid-Open No. 55-148775

SUMMARY OF INVENTION Technical Problem

When electrolysis operation is started and continued, each partdeteriorates and electrolytic performance are lowered due to variousfactors, and each part is replaced at a certain time point. The membranecan be easily renewed by extracting from an electrolytic cell andinserting a new membrane. In contrast, the anode and the cathode arefixed to the electrolytic cell, and thus, there is a problem ofoccurrence of an extremely complicated work on renewing the electrode,in which the electrolytic cell is removed from the electrolyzer andconveyed to a dedicated renewing plant, fixing such as welding isremoved and the old electrode is striped off, then a new electrode isplaced and fixed by a method such as welding, and the cell is conveyedto the electrolysis plant and placed back to the electrolyzer. It isconsidered herein that the structure formed by integrating a membraneand an electrode via thermal compression described in Patent Literatures1 and 2 is used for the renewing described above, but the structure,which can be produced at a laboratory level relatively easily, is noteasily produced so as to be adapted to an electrolytic cell in an actualcommercially-available size (e.g., 1.5 m in length, 3 m in width).Moreover, electrolytic performance (such as electrolysis voltage,current efficiency, and common salt concentration in caustic soda) anddurability are extremely poor, and chlorine gas and hydrogen gas aregenerated on the electrode interfacing the membrane. Thus, when used inelectrolysis for a long period, complete delamination occurs, and thestructure cannot be practically used.

The present invention has been made in view of the above problemspossessed by the conventional art and is intended to provide anelectrode for electrolysis, a laminate, a wound body, an electrolyzer, amethod for producing an electrolyzer, a method for renewing anelectrode, a method for renewing a laminate, and a method for producinga wound body below.

(First Object)

It is an object of the present invention provide an electrode forelectrolysis, a laminate, and a wound body that make transport andhandling easier, markedly simplify a work when a new electrolyzer isstarted or a degraded electrode is renewed, and furthermore also canmaintain or improve the electrolytic performance.

(Second Object)

It is an object of the present invention to provide a laminate that canimprove the work efficiency during electrode renewing in an electrolyzerand further can exhibit excellent electrolytic performance also afterrenewing.

(Third Object)

It is an object of the present invention to provide a laminate that canimprove the work efficiency during electrode renewing in an electrolyzerand further can exhibit excellent electrolytic performance also afterrenewing, from a viewpoint different from the second object describedabove.

(Fourth Object)

It is a fourth object of the present invention to provide anelectrolyzer, a method for producing an electrolyzer, and a method forrenewing a laminate that have excellent electrolytic performance as wellas can prevent damage of a membrane.

(Fifth Object)

It is an object of the present invention to provide a method forproducing an electrolyzer, a method for renewing an electrode, and amethod for producing a wound body that can improve the work efficiencyduring electrode renewing in an electrolyzer.

(Sixth Object)

It is an object of the present invention to provide a method forproducing an electrolyzer that can improve the work efficiency duringelectrode renewing in an electrolyzer, from a viewpoint different fromthe fifth object described above.

(Seventh Object)

It is an object of the present invention to provide a method forproducing an electrolyzer that can improve the work efficiency duringelectrode renewing in an electrolyzer, from a viewpoint different fromthe fifth and sixth objects described above.

Solution to Problem

As a result of the intensive studies by the present inventors to achievethe first object, production of an electrode for electrolysis that has asmall mass per unit area and can be bonded to a membrane such as an ionexchange membrane and a microporous membrane or a degraded electrodewith a weak force makes transport and handling easer, can markedlysimplify a work when a new electrolyzer is started or a degraded part isrenewed, and furthermore can markedly improve the characteristics incomparison with the electrolytic performance in the conventional art.Additionally, the present inventors have found that the characteristicscan be equivalent to or be improved than the electrolytic performance ofa conventional electrolytic cell, for which renewing work iscomplicated, thereby having completed the present invention.

That is, the present invention includes the following.

[1]

An electrode for electrolysis having a mass per unit area of 48 mg/cm²or less and a force applied per unit mass·unit area of 0.08 N/mg·cm² ormore.

[2]

The electrode for electrolysis according to [1], wherein the electrodefor electrolysis comprises a substrate for electrode for electrolysisand a catalytic layer, and the substrate for electrode for electrolysishas a thickness of 300 μm or less.

[3]

The electrode for electrolysis according to [1] or [2], wherein aproportion measured by a method (3) below is 75% or more:

[Method (3)]

A membrane (170 mm square), which is obtained by applying inorganicmaterial particles and a binder to both surfaces of a membrane of aperfluorocarbon polymer into which an ion exchange group is introduced,and a sample of electrode for electrolysis (130 mm square) are laminatedin this order; and the laminate is placed on a curved surface of apolyethylene pipe (outer diameter: 145 mm; such that the sample ofelectrode for electrolysis in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then a proportion (%) ofan area of a portion, in which the sample of electrode for electrolysisis in close contact with the membrane obtained by applying the inorganicmaterial particles and the binder to both the surfaces of the membraneof the perfluorocarbon polymer into which the ion exchange group isintroduced, is measured.

[4]

The electrode for electrolysis according to any of [1] to [3], whereinthe electrode for electrolysis has a porous structure and has an openingratio of 5 to 90%.

[5]

The electrode for electrolysis according to any of [1] to [4], whereinthe electrode has a porous structure and has an opening ratio of 10 to80%.

[6]

The electrode for electrolysis according to any of [1] to [5], whereinthe electrode for electrolysis has a thickness of 315 μm or less.

[7]

The electrode for electrolysis according to any of [1] to [6], wherein avalue obtained by measuring the electrode for electrolysis by a methodbelow is 40 mm or less:

[Method (A)]

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, a sample obtained by laminating the ion exchange membrane and theelectrode for electrolysis is wound around and fixed onto a curvedsurface of a core material being made of polyvinyl chloride and havingan outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter,when the electrode for electrolysis is separated from the sample an1placed on a flat plate, heights in a vertical direction at both edges ofthe electrode for electrolysis L₁ and L₂ are measured, and an averagevalue thereof is used as a measurement value.

[8]

The electrode for electrolysis according to any one of [1] to [7],wherein a ventilation resistance is 24 kPa·s/m or less when theelectrode for electrolysis has a size of 50 mm×50 mm, the ventilationresistance being measured under conditions of the temperature of 24° C.,the relative humidity of 32%, a piston speed of 0.2 cm/s, and aventilation volume of 0.4 cc/cm²/s.

[9]

The electrode for electrolysis according to any of [1] to [8], whereinthe electrode comprises at least one element selected from nickel (Ni)and titanium (Ti).

[10]

A laminate comprising the electrode for electrolysis according to any of[1] to [9].

[11]

A wound body comprising the electrode for electrolysis according to anyof [1] to [9] or the laminate according to [10].

As a result of the intensive studies to achieve the second object, thepresent inventors have found that a laminate that includes an electrodeto be bonded to a membrane such as an ion exchange membrane and amicroporous membrane and to a feed conductor such as a degraded existingelectrode with a weak force makes transport and handling easier, canmarkedly simplify a work when a new electrolyzer is started or adegraded part is renewed, and furthermore can also maintain or improvethe electrolytic performance, thereby having completed the presentinvention.

That is, the present invention includes the following aspects.

[2-1]

A laminate comprising:

an electrode for electrolysis, and

a membrane or feed conductor in contact with the electrode forelectrolysis,

wherein a force applied per unit mass·unit area of the electrode forelectrolysis on the membrane or feed conductor is less than 1.5N/mg·cm².

[2-2]

The laminate according to [2-1], wherein the force applied per unitmass'unit area of the electrode for electrolysis on the membrane or feedconductor is more than 0.005 N/mg·cm².

[2-3]

The laminate according to [2-1] or [2-2], wherein the feed conductor isa wire mesh, a metal nonwoven fabric, a perforated metal, an expandedmetal, or a foamed metal.

[2-4]

The laminate according to any of [2-1] to [2-3], comprising, as at leastone surface layer of the membrane, a layer comprising a mixture ofhydrophilic oxide particles and a polymer into which ion exchange groupsare introduced.

[2-5]

The laminate according to any of [2-1] to [2-4], wherein a liquid isinterposed between the electrode for electrolysis and the membrane orfeed conductor.

As a result of the intensive studies to achieve the third object, thepresent inventors have found that the problems described above can besolved by a laminate in which a membrane and an electrode forelectrolysis are partially fixed, thereby having completed the presentinvention.

That is, the present invention includes the following aspects.

[3-1]

A laminate comprising:

a membrane, and

an electrode for electrolysis fixed in at least one region of a surfaceof the membrane,

wherein a proportion of the region on the surface of the membrane ismore than 0% and less than 93%.

[3-2]

The laminate according to [3-1], wherein the electrode for electrolysiscomprises at least one catalytic component selected from the groupconsisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O,Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy.

[3-3]

The laminate according to [3-1] or [3-2], wherein at least a portion ofthe electrode for electrolysis penetrates the membrane and thereby isfixed in the region.

[3-4]

The laminate according to any one of [3-1] to [3-3], wherein at least aportion of the electrode for electrolysis is located inside the membraneand thereby fixed in the region.

[3-5]

The laminate according to any one of [3-1] to [3-4], further comprisinga fixing member for fixing the membrane and the electrode forelectrolysis.

[3-6]

The laminate according to [3-5], wherein at least a portion of thefixing member externally grips the membrane and the electrode forelectrolysis.

[3-7]

The laminate according to [3-5] or [3-6], wherein at least a portion ofthe fixing member fixes the membrane and the electrode for electrolysisby magnetic force.

[3-8]

The laminate according to any one of [3-1] to [3-7], wherein

the membrane comprises an ion exchange membrane comprising a surfacelayer comprising an organic resin, and

the organic resin is present in the region.

[3-9]

The laminate according to any one of [3-1] to [3-8], wherein themembrane comprises a first ion exchange resin layer and a second ionexchange resin layer having an EW different from that of the first ionexchange resin layer.

[3-10]

The laminate according to any one of [3-1] to [3-8], wherein themembrane comprises a first ion exchange resin layer and a second ionexchange resin layer having a functional group different from that ofthe first ion exchange resin layer.

As a result of the intensive studies to achieve the fourth object, thepresent inventors have found that the problems described above can besolved by sandwiching at least a portion of a laminate of a membrane andan electrode for electrolysis between an anode side gasket and a cathodeside gasket, thereby having completed the present invention.

That is, the present invention includes the following aspects.

[4-1]

An electrolyzer comprising:

an anode,

an anode frame that supports the anode,

an anode side gasket that is arranged on the anode frame,

a cathode that is opposed to the anode,

a cathode frame that supports the cathode,

a cathode side gasket that is arranged on the cathode frame and isopposed to the anode side gasket, and

a laminate of a membrane and an electrode for electrolysis, the laminatebeing arranged between the anode side gasket and the cathode sidegasket,

wherein at least a portion of the laminate is sandwiched between theanode side gasket and the cathode side gasket, and

a ventilation resistance is 24 kPa·s/m or less when the electrode forelectrolysis has a size of 50 mm×50 mm, the ventilation resistance beingmeasured under conditions of a temperature of 24° C., a relativehumidity of 32%, a piston speed of 0.2 cm/s, and a ventilation volume of0.4 cc/cm²/s.

[4-2]

The electrolyzer according to [4-1], wherein the electrode forelectrolysis has a thickness of 315 μm or less.

[4-3]

The electrolyzer according to [4-1] or [4-2], wherein a value obtainedby measuring the electrode for electrolysis by a method (A) below is 40mm or less:

[4-Method (A)]

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, a sample obtained by laminating the ion exchange membrane and theelectrode for electrolysis is wound around and fixed onto a curvedsurface of a core material being made of polyvinyl chloride and havingan outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter,when the electrode for electrolysis is separated from the sample andplaced on a flat plate, heights in a vertical direction at both edges ofthe electrode for electrolysis L1 and L2 are measured, and an averagevalue thereof is used as a measurement value.

[4-4]

The electrolyzer according to any of [4-1] to [4-3], wherein a mass perunit area of the electrode for electrolysis is 48 mg/cm² or less.

[4-5]

The electrolyzer according to any of [4-1] to [4-4], wherein a forceapplied per unit mass·unit area of the electrode for electrolysis ismore than 0.005 N/mg·cm².

[4-6]

The electrolyzer according to any of [4-1] to [4-5], wherein anoutermost perimeter of the laminate is located farther outside than anoutermost perimeter each of the anode side gasket and the cathode sidegasket in a direction of a conducting surface.

[4-7]

The electrolyzer according to any of [4-1] to [4-6], wherein theelectrode for electrolysis comprises at least one catalytic componentselected from the group consisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn,Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,and Dy.

[4-8]

The electrolyzer according to any of [4-1] to [4-7], wherein at least aportion of the electrode for electrolysis penetrates the membrane andthereby is fixed in the laminate.

[4-9]

The electrolyzer according to any of [4-1] to [4-7], wherein at least aportion of the electrode for electrolysis is located inside the membraneand thereby fixed in the laminate.

[4-10]

The electrolyzer according to any of [4-1] to [4-9], wherein thelaminate further comprises a fixing member for fixing the membrane andthe electrode for electrolysis.

[4-11]

The electrolyzer according to [4-10], wherein, in the laminate, at leasta portion of the fixing member penetrates and thereby fixes the membraneand the electrode for electrolysis.

[4-12]

The electrolyzer according to [4-10] or [4-11], wherein, in thelaminate, the fixing member comprises a soluble material that is solublein a electrolyte solution.

[4-13]

The electrolyzer according to any of [4-10] to [4-12], wherein, in thelaminate, at least a portion of the fixing member externally grips themembrane and the electrode for electrolysis.

[4-14]

The electrolyzer according to any of [4-10] to [4-13], wherein, in thelaminate, at least a portion of the fixing member fixes the membrane andthe electrode for electrolysis by magnetic force.

[4-15]

The electrolyzer according to any of [4-1] to [4-14], wherein

the membrane comprises an ion exchange membrane comprising a surfacelayer comprising an organic resin, and

the electrode for electrolysis is fixed by the organic resin.

[4-16]

The electrolyzer according to any of [4-1] to [4-15], wherein themembrane comprises a first ion exchange resin layer and a second ionexchange resin layer having an EW different from that of the first ionexchange resin layer.

[4-17]

A method for producing the electrolyzer according to any of [4-1] to[4-16], the method comprising:

a step of sandwiching the laminate between the anode side gasket and thecathode side gasket.

[4-18]

A method for renewing the laminate in the electrolyzer according to anyof [4-1] to [4-16], the method comprising:

a step of separating the laminate from the anode side gasket and thecathode side gasket to thereby remove the laminate from theelectrolyzer, and

a step of sandwiching a new laminate between the anode side gasket andthe cathode side gasket.

As a result of the intensive studies to achieve the fifth object, thepresent inventors have found that the problems described above can besolved by use of an electrode for electrolysis or a laminate of theelectrode for electrolysis and a new membrane, being in a wound bodyform, thereby having completed the present invention.

That is, the present invention includes the following aspects.

[5-1]

A method for producing a new electrolyzer by arranging an electrode forelectrolysis or a laminate of the electrode for electrolysis and a newmembrane in an existing electrolyzer comprising an anode, a cathode thatis opposed to the anode, and a membrane that is arranged between theanode and the cathode,

wherein the electrode for electrolysis or the laminate, being in a woundbody form, is used.

[5-2]

The method for producing the electrolyzer according to [5-1], comprisinga step (A) of retaining the electrode for electrolysis or the laminatein a wound state to thereby obtain the wound body.

[5-3]

The method for producing the electrolyzer according to [5-1] or [5-2],comprising a step (B) of releasing the wound state of the wound body.

[5-4]

The method for producing the electrolyzer according to [5-3], comprisinga step (C) of arranging the electrode for electrolysis or the laminateon a surface of at least one of the anode and the cathode after the step(B).

[5-5]

A method for renewing an existing electrode by using an electrode forelectrolysis,

wherein the electrode for electrolysis being in a wound body form isused.

[5-6]

The method for renewing the electrode according to [5-5], comprising astep (A′) of retaining the electrode for electrolysis in a wound stateto thereby obtain the wound body.

[5-7]

The method for renewing the electrode according to [5-5] or [5-6],comprising a step (B′) of releasing the wound state of the wound body.

[5-8]

The method for renewing the electrode according to [5-7], comprising astep (C′) of arranging the electrode for electrolysis on a surface ofthe existing electrode after the step (B′).

[5-9]

A method for producing a wound body to be used for renewing an existingelectrolyzer comprising an anode, a cathode that is opposed to theanode, and a membrane that is arranged between the anode and thecathode, the method comprising:

a step of winding an electrode for electrolysis or a laminate of theelectrode for electrolysis and a new membrane to thereby obtain thewound body.

As a result of the intensive studies to achieve the sixth object, thepresent inventors have found that the problems described above can besolved by integrating an electrode for electrolysis with a new membraneat a temperature at which the membrane does not melt, thereby havingcompleted the present invention.

That is, the present invention includes the following aspects.

[6-1]

A method for producing a new electrolyzer by arranging a laminate in anexisting electrolyzer comprising an anode, a cathode that is opposed tothe anode, and a membrane that is arranged between the anode and thecathode, the method comprising:

a step (A) of integrating an electrode for electrolysis with a newmembrane at a temperature at which the membrane does not melt to therebyobtain the laminate, and

a step (B) of replacing the membrane in the existing electrolyzer by thelaminate after the step (A).

[6-7]

The method for producing the electrolyzer according to [6-1], whereinthe integration is carried out under normal pressure.

As a result of the intensive studies to achieve the seventh object, thepresent inventors have found that the problems described above can besolved by an operation in an electrolyzer frame, thereby havingcompleted the present invention.

That is, the present invention includes the following aspects.

[7-1]

A method for producing a new electrolyzer by arranging a laminatecomprising an electrode for electrolysis and a new membrane in anexisting electrolyzer comprising an anode, a cathode that is opposed tothe anode, a membrane that is fixed between the anode and the cathode,and an electrolyzer frame that supports the anode, the cathode, and themembrane, the method comprising:

a step (A) releasing a fixing of the membrane in the electrolyzer frame,and

a step (B) of replacing the membrane by the laminate after the step (A).

[7-2]

The method for producing the electrolyzer according to [7-1], whereinthe step (A) is carried out sliding the anode and the cathode in anarrangement direction thereof, respectively.

[7-3]

The method for producing the electrolyzer according to [7-1] or [7-2],wherein the laminate is fixed in the electrolyzer frame by pressing fromthe anode and the cathode after the step (B).

[7-4]

The method for producing the electrolyzer according to any of [7-1] to[7-3], wherein the laminate is fixed on a surface of at least one of theanode and the cathode at a temperature at which the laminate does notmelt in the step (B).

[7-5]

A method for producing a new electrolyzer by arranging an electrode forelectrolysis in an existing electrolyzer comprising an anode, a cathodethat is opposed to the anode, a membrane that is fixed between the anodeand the cathode, and an electrolyzer frame that supports the anode, thecathode, and the membrane, the method comprising:

a step (A) of releasing a fixing of the membrane in the electrolyzerframe, and

a step (B′) of arranging the electrode for electrolysis between themembrane and the anode or the cathode after the step (A).

Advantageous Effects of Invention

(1) According to the electrode for electrolysis of the presentinvention, it is possible to make transport and handling easier, tomarkedly simplify a work when a new electrolyzer is started or adegraded electrode is renewed, and furthermore, to also maintain orimprove the electrolytic performance.

(2) According to the laminate of the present invention, it is possibleto improve the work efficiency during electrode renewing in anelectrolyzer and furthermore, to exhibit excellent electrolyticperformance also after renewing.

(3) According to the laminate of the present invention, it is possibleto improve the work efficiency during electrode renewing in anelectrolyzer and further, to develop excellent electrolytic performancealso after renewing, from a viewpoint different from (2) described,above.

(4) According to electrolyzer of the present invention, the electrolyzerhas excellent electrolytic performance as well as can prevent damage ofthe membrane.

(5) According to the method for producing an electrolyzer of the presentinvention, it is possible to improve the work efficiency duringelectrode renewing in an electrolyzer.

(6) According to the method for producing an electrolyzer of the presentinvention, it is possible to improve the work efficiency duringelectrode renewing in an electrolyzer, from a viewpoint different from(5) described above.

(7) According to the method for producing an electrolyzer of the presentinvention, it is possible to improve the work efficiency duringelectrode renewing in an electrolyzer, from a viewpoint different from(5) and (6) described above.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 illustrates a cross-sectional schematic view of an electrode forelectrolysis according to one embodiment of the present invention.

FIG. 2 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane.

FIG. 3 illustrates a schematic view for explaining the aperture ratio ofreinforcement core materials constituting the ion exchange membrane.

FIG. 4 illustrates a schematic view for explaining a method for formingthe continuous holes of the ion exchange membrane.

FIG. 5 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 6 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 7 illustrates a schematic view of an electrolyzer.

FIG. 8 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 9 illustrates a cross-sectional schematic view of a reverse currentabsorber included in the electrolytic cell.

FIG. 10 illustrates a schematic view of a method for evaluating a forceapplied per unit mass·unit area (1) described in Examples.

FIG. 11 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (1) described in Examples.

FIG. 12 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (2) described in Examples.

FIG. 13 illustrates a schematic view of a method for evaluating windingaround a column of 145 mm in diameter (3) described in Examples.

FIG. 14 illustrates a schematic view of elastic deformation test of theelectrode described is Examples.

FIG. 15 illustrates a schematic view of a method for evaluating softnessafter plastic deformation.

FIG. 16 illustrates a schematic view of an electrode produced inComparative Example 13.

FIG. 17 illustrates a schematic view of a structure used for placing theelectrode produced in Comparative Example 13 on a nickel mesh feedconductor.

FIG. 18 illustrates a schematic view of an electrode produced inComparative Example 14.

FIG. 19 illustrates a schematic view of a structure used for placing theelectrode produced in Comparative Example 14 on a nickel mesh feedconductor.

FIG. 20 illustrates a schematic view of an electrode produced inComparative Example 15.

FIG. 21 illustrates a schematic view of a structure used for placing theelectrode produced in Comparative Example 15 on a nickel mesh feedconductor.

FIG. 22 illustrates a cross-sectional schematic view of an electrode forelectrolysis in one embodiment of the present invention.

FIG. 23 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane.

FIG. 24 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 25 illustrates a schematic view for explaining a method for formingthe continuous holes of the ion exchange membrane.

FIG. 26 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 27 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 28 illustrates a schematic view of an electrolyzer.

FIG. 29 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 30 illustrates a cross-sectional schematic view of a reversecurrent absorber included in the electrolytic cell.

FIG. 31 illustrates a schematic view of a method for evaluating a forceapplied per unit mass·unit area (1) described in Examples.

FIG. 32 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (1) described in Examples.

FIG. 33 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (2) described in Examples.

FIG. 34 illustrates a schematic view of a method for evaluating windingaround a column of 145 mm in diameter (3) described in Examples.

FIG. 35 illustrates a schematic view of elastic deformation test of theelectrode described in Examples.

FIG. 36 illustrates a schematic view of a method for evaluating softnessafter plastic deformation.

FIG. 37 illustrates a schematic view of an electrode produced in Example34.

FIG. 38 illustrates a schematic view of a structure used for placing theelectrode produced in Example 34 on a nickel mesh feed conductor.

FIG. 39 illustrates a schematic view of an electrode produced in Example35.

FIG. 40 illustrates a schematic view of a structure used for placing theelectrode produced in Example 35 on a nickel mesh feed conductor.

FIG. 41 illustrates a schematic view of an electrode produced in Example36.

FIG. 42 illustrates a schematic view of a structure used for placing theelectrode produced in Example 36 on a nickel mesh feed conductor.

FIG. 43 illustrates a cross-sectional schematic view of an electrode forelectrolysis in one embodiment of the present invention.

FIG. 44 illustrates a cross-sectional schematic view illustrating oneembodiment of an ion exchange membrane.

FIG. 45 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 46 illustrates a schematic view for explaining a method for formingthe continuous holes of the ion exchange membrane.

FIG. 47A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of an electrode forelectrolysis penetrates a membrane and thereby is fixed. FIG. 47Billustrates an explanatory view illustrating a step of obtaining thestructure of FIG. 47A.

FIG. 48A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of an electrode forelectrolysis is located inside the membrane and thereby fixed. FIG. 48Billustrates an explanatory view illustrating a step of obtaining thestructure of FIG. 48A.

FIGS. 49A to 49C illustrate cross-sectional schematic views of alaminate illustrating an aspect in which a yarn-like fixing member isused for fixing as a fixing member for fixing a membrane and anelectrode for electrolysis.

FIG. 50 illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which an organic resin is used for fixing as afixing member for fixing a membrane and an electrode for electrolysis.

FIG. 51A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of a fixing memberexternally grips a membrane and an electrode for electrolysis to fixthem. FIG. 51B illustrates a cross-sectional schematic view of thelaminate illustrating an aspect in which at least a portion of a fixingmember fixes the membrane and the electrode for electrolysis by magneticforce.

FIG. 52 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 53 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 54 illustrates a schematic view of an electrolyzer.

FIG. 55 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 56 illustrates a cross-sectional schematic view of a reversecurrent absorber that may be included in an electrolytic cell.

FIG. 57 illustrates an explanatory view showing a laminate in Example 1.

FIG. 58 illustrates an explanatory view showing a laminate in Example 2.

FIG. 59 illustrates an explanatory view showing a laminate in Example 3.

FIG. 60 illustrates an explanatory view showing a laminate in Example 4.

FIG. 61 illustrates an explanatory view showing a laminate in Example 5.

FIG. 62 illustrates an explanatory view showing a laminate in Example 6.

FIG. 63 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 64A illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series in a conventionalelectrolyzer.

FIG. 64B illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series in the electrolyzer of thepresent embodiment.

FIG. 65 illustrates a schematic view of an electrolyzer.

FIG. 66 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 67 illustrates a cross-sectional schematic view of a reversecurrent absorber that may be included in an electrolytic cell.

FIG. 68 illustrates a cross-sectional schematic view of an electrode forelectrolysis in one embodiment of the present invention.

FIG. 69 illustrates a cross-sectional schematic view illustrating oneembodiment of an ion exchange membrane.

FIG. 70 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 71 illustrates a schematic view for explaining a method for formingthe continuous holes of the ion exchange membrane.

FIG. 72 illustrates an explanatory view for explaining the positionalrelation between the laminate and the gaskets.

FIG. 73 illustrates an explanatory view for explaining the positionalrelation between the laminate and the gaskets.

FIG. 74A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of an electrode forelectrolysis penetrates a membrane and thereby is fixed. FIG. 74Billustrates an explanatory view illustrating a step of obtaining thestructure of FIG. 12A.

FIG. 75A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of an electrode forelectrolysis located inside the membrane and thereby fixed. FIG. 13Billustrates an explanatory view illustrating a step of obtaining thestructure of FIG. 75A.

FIGS. 76A to C illustrate cross-sectional schematic views of a laminateillustrating an aspect in which a yarn-like fixing member is used forfixing as a fixing member for fixing a membrane and an electrode forelectrolysis.

FIG. 77 illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which an organic resin is used for fixing as afixing member for fixing a membrane and an electrode for electrolysis.

FIG. 78A illustrates a cross-sectional schematic view of a laminateillustrating an aspect in which at least a portion of a fixing memberexternally grips a membrane and an electrode for electrolysis to fixthem. FIG. 78B illustrates a cross-sectional schematic view of thelaminate illustrating an aspect in which at least a portion of a fixingmember fixes the membrane and the electrode for electrolysis by magneticforce.

FIG. 79 illustrates a schematic view of a method for evaluating a forceapplied per unit mass·unit area (1) described in Examples.

FIG. 80 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (1) described in Examples.

FIG. 81 illustrates a schematic view of a method for evaluating windingaround a column of 280 mm in diameter (2) described in Examples.

FIG. 82 illustrates a schematic view of a method for evaluating windingaround a column of 145 mm in diameter (3) described in Examples.

FIG. 83 illustrates a schematic view of flexibility evaluation of theelectrode described in Examples.

FIG. 84 illustrates a schematic view of a method for evaluating softnessafter plastic deformation.

FIG. 85 illustrates a schematic view of an electrode produced in Example35.

FIG. 86 illustrates a schematic view of a structure used for placing theelectrode produced in Example 35 on a nickel mesh feed conductor.

FIG. 87 illustrates a schematic view of an electrode produced in Example36.

FIG. 88 illustrates a schematic view of a structure used for placing theelectrode produced in Example 36 on a nickel mesh feed conductor.

FIG. 89 illustrates a schematic view of an electrode produced in Example37.

FIG. 90 illustrates a schematic view of a structure used for placing theelectrode produced in Example 37 on a nickel mesh feed conductor.

FIG. 91 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 92 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 9a illustrates a schematic view of an electrolyzer.

FIG. 94 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 95 illustrates a cross-sectional schematic view of a reversecurrent absorber that may be included in an electrolytic cell.

FIG. 96 illustrates a cross-sectional schematic view of an electrode forelectrolysis in one embodiment of the present invention.

FIG. 97 illustrates a cross-sectional schematic view illustrating oneembodiment of an ion exchange membrane.

FIG. 98 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 99 illustrates a schematic view for explaining a method for formingthe continuous holes of the ion exchange membrane.

FIG. 100 illustrates a schematic view of a laminate produced in Example1.

FIG. 101 illustrates a schematic view of the case where the laminateproduced in Example 1 is wound to form a wound body.

FIG. 102 illustrates a schematic view of a laminate produced in Example4.

FIG. 103 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 104 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 105 illustrates a schematic view of an electrolyzer.

FIG. 106 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 107 illustrates a cross-sectional schematic view of a reversecurrent absorber that may be included in an electrolytic cell.

FIG. 108 illustrates a cross-sectional schematic view of an electrodefor electrolysis in one embodiment of the present invention.

FIG. 109 illustrates a cross-sectional schematic view illustrating oneembodiment of an ion exchange membrane.

FIG. 110 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 111 illustrates a schematic view for explaining a method forforming the continuous holes of the ion exchange membrane.

FIG. 112 illustrates a cross-sectional schematic view of an electrolyticcell.

FIG. 113 illustrates a cross-sectional schematic view showing a state oftwo electrolytic cells connected in series.

FIG. 114 illustrates a schematic view of an electrolyzer.

FIG. 115 illustrates a schematic perspective view showing a step ofassembling the electrolyzer.

FIG. 116 illustrates a cross-sectional schematic view of a reversecurrent absorber that may be included in an electrolytic cell.

FIG. 117(A) illustrates a schematic view of an electrolyzer forexplaining one example of each step according to a first aspect of thepresent embodiment. FIG. 117(B) illustrates a schematic perspective viewcorresponding to FIG. 117(A).

FIG. 118(A) illustrates a schematic view of an electrolyzer forexplaining one example of each step according to a second aspect of thepresent embodiment. FIG. 118(B) illustrates a schematic perspective viewcorresponding to FIG. 118(A).

FIG. 119 illustrates a cross-sectional schematic view of an electrodefor electrolysis in one embodiment of the present invention.

FIG. 120 illustrates a cross-sectional schematic view illustrating oneembodiment of an ion exchange membrane.

FIG. 121 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.

FIG. 122 illustrates a schematic view for explaining a method forforming the continuous holes of the ion exchange membrane.

DESCRIPTION OF EMBODIMENTS

Hereinbelow, as for embodiments of the present invention (hereinbelow,may be referred to as the present embodiments), <First embodiment> to<Seventh embodiment> will be each described in detail, with reference todrawings as required. The embodiments below are illustration forexplaining the present invention, and the present invention is notlimited to the contents below. The accompanying drawings illustrate oneexample of the embodiments, and embodiments should not be construed tobe limited thereto. The present invention may be appropriately modifiedand carried out within the spirit thereof. In the drawings, positionalrelations such as top, bottom, left, and right are based on thepositional relations shown in the drawing unless otherwise noted. Thedimensions and ratios in the drawings are not limited to those shown.

First Embodiment

Here, a first embodiment of the present invention will be described indetail with reference to FIGS. 1 to 21.

[Electrode for Electrolysis]

An electrode for electrolysis of the first embodiment (hereinafter, inthe section of <First embodiment>, simply referred to as “the presentembodiment”) can provide a good handling property, has a good adhesiveforce to a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, and further, has a mass per unit area of 48mg/cm² or less from the viewpoint of economy. The mass per unit area ispreferably 30 mg/cm² or less, further preferably 20 mg/cm² or less inrespect of the above, and furthermore is preferably 15 mg/cm² or lessfrom the comprehensive viewpoint including handling property, adhesion,and economy. The lower limit value is not particularly limited but is ofthe order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The electrode for electrolysis of the present embodiment has a forceapplied per unit mass·unit area of 0.08 N/(mg·cm²) or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and the like. The force applied per unit mass·unitarea is preferably 0.1 N/(mg·cm²) or more, more preferably 0.14N/(mg·cm²) or more in respect of the above, and more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value isnot particularly limited, but is preferably 1.6 N/(mg·cm²) or less, morepreferably less than 1.6 N/(mg·cm²), further preferably less than 1.5N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less. The upper limit value is even stillmore preferably 1.1 N/mg·cm² or less, further still more preferably 1.10N/mg·cm² or less, particularly preferably 1.0 N/mg·cm² or less,especially preferably 1.00 N/mg·cm² or less.

From the viewpoint that the electrode for electrolysis of the presentembodiment, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness of 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

The electrode for electrolysis of the present embodiment, which has agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and the like, as described above, can be integratedwith a membrane such as an ion exchange membrane and a microporousmembrane and used. For this reason, on renewing the electrode, theelectrode can he renewed by a work as simple as renewing the membrane,without a complicated substituting work such as stripping off theelectrode fixed on the electrolytic cell, and thus, the work efficiencyis markedly improved. Even in the case where only a feed conductor isplaced in a new electrolytic cell (i.e., an electrode including nocatalyst layer placed), only attaching the electrode for electrolysis ofthe present embodiment to the feed conductor enables the electrode tofunction. Thus, it may be also possible to markedly reduce or eliminatecatalyst coating.

Further, according to the electrode for electrolysis of the presentembodiment, it is possible to make the electrolytic performancecomparable to or higher than those of a new electrode.

The electrode for electrolysis of the present embodiment can be storedor transported to customers in a state where the electrode wound arounda vinyl chloride pipe or the like (in a rolled state or the like),making handling markedly easier.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as described in Examples in detail. As for the forceapplied, the value obtained by the measurement of the method (i) (alsoreferred to as “the force applied (1)”) and the value obtained by themeasurement of the method (ii) (also referred to as “the force applied(2)”) may be the same or different, and either of the values is 0.08N/(mg·cm²) or more.

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode for electrolysis (130 mm square) are laminatedin this order. After this laminate is sufficiently immersed in purewater, excess water deposited on the surface of the laminate is removedto obtain a sample for measurement. The arithmetic average surfaceroughness (Ra) of the nickel plate after the blast treatment was 0.7 μm.The specific method for calculating the arithmetic average surfaceroughness (Ra) is as described in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode for electrolysis in this sample formeasurement is raised in a vertical direction at 10 mm/minute using atensile and compression testing machine, and the load when the sample ofelectrode for electrolysis is raised by 10 mm in a vertical direction ismeasured. This measurement is repeated three times, and the averagevalue is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode for electrolysis and the ion exchange membraneand the mass of the portion overlapping the ion exchange membrane in thesample of electrode for electrolysis to calculate the force applied perunit mass·unit area (1) (N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method is0.08 N/(mg·cm²) or more, preferably 0.1 N/(mg·cm²) or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode, and a feed conductorhaving no catalyst coating, and more preferably 0.2 N/(mg·cm²) or morefrom the viewpoint of further facilitating handling in a large size(e.g., a size of 1.5 m×2.5 m). The upper limit value is not particularlylimited, but is preferably 1.6 N/(mg·cm²) or less, more preferably lessthan 1.6 N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), evenfurther preferably 1.2 N/mg·cm² or less, still more preferably 1.20N/mg·cm² or less. The upper limit value is even still more preferably1.1 N/mg·cm ² or less, further still more preferably 1.10 N/mg·cm² orless, particularly preferably 1.0 N/mg·cm² or less, especiallypreferably 1.00 N/mg·cm² or less.

When the electrode for electrolysis of the present embodiment satisfiesthe force applied (1), the electrode can be integrated with a membranesuch as an ion exchange membrane and a microporous membrane, forexample, and used. Thus, on renewing the electrode, the substitutingwork for the cathode and anode fixed on the electrolytic cell by amethod such as welding is eliminated, and the work efficiency ismarkedly improved. Additionally, by use of the electrode forelectrolysis of the present embodiment as an electrode integrated withthe ion exchange membrane, it is possible to make the electrolyticperformance comparable to or higher than those of a new electrode.

On shipping a new electrolytic cell, an electrode fixed on anelectrolytic cell has been subjected to catalyst coating conventionally.Since only combination of an electrode having no catalyst coating withthe electrode for electrolysis of the present embodiment can allow theelectrode to function as an electrode, it is possible to markedly reduceor eliminate the production step and the amount of the catalyst forcatalyst coating. A conventional electrode of which catalyst coating ismarkedly reduced or eliminated can be electrically connected to theelectrode for electrolysis of the present embodiment and allowed toserve as a feed conductor for passage of an electric current.

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode for electrolysis(130 mm square) are laminated in this order. After this laminate issufficiently immersed in pure water, excess water deposited on thesurface of the laminate is removed to obtain a sample for measurement.Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode for electrolysis in this sample formeasurement is raised in a vertical direction at 10 mm/minute using atensile and compression testing machine, and the load when the sample ofelectrode for electrolysis is raised by 10 mm in a vertical direction ismeasured. This measurement is repeated three times, and the averagevalue is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode for electrolysis and the nickel plate and themass of the sample of electrode for electrolysis in the portionoverlapping the nickel plate to calculate the adhesive force per unitmass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is 0.08 N/(mg·cm²) or more, preferably 0.1 N/(mg·cm²) or more fromthe viewpoint of enabling a good handling property to be provided andhaving a good adhesive force to a membrane such as an ion exchangemembrane and a microporous membrane, a degraded electrode, and a feedconductor having no catalyst coating, and more preferably 0.14N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m). The upper limit value isnot particularly limited, but is preferably 1.6 N/(mg·cm²) or less, morepreferably less than 1.6 N/(mg·cm²), further preferably less than 1.5N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less. The upper limit value is even stillmore preferably 1.1 N/mg·cm² or less, further still more preferably 1.10N/mg·cm² or less, particularly preferably 1.0 N/mg·cm² or less,especially preferably 1.00 N/mg·cm² or less.

The electrode for electrolysis of the present embodiment, if satisfiesthe force applied (2), can be stored or transported to customers in astate where the electrode is wound around a vinyl chloride pipe or thelike (in a rolled state or the like), making handling markedly easier.By attaching, the electrode for electrolysis of the present embodimentto a degraded electrode, it is possible to make the electrolyticperformance comparable to or higher than those of a new electrode.

In the present embodiment, as the liquid included between the membranesuch as an ion exchange membrane and a macroporous membrane, theelectrode for electrolysis or the feed conductor (degraded electrode orelectrode having no catalyst coating) and the electrode forelectrolysis, any liquid, such as water and organic solvents, can beused as long as the liquid generates a surface tension. The larger thesurface tension of the liquid, the larger the force applied between themembrane and the electrode for electrolysis or the metal plate and theelectrode for electrolysis. Thus, a liquid having a larger surfacetension is preferred. Examples of the liquid include the following (thenumerical value in the parentheses is the surface tension of theliquid):

hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00 mN/m),ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and water (72.76mN/m).

A liquid having a large surface tension allows the membrane and theelectrode for electrolysis or the metal porous plate or metal plate(feed conductor) and the electrode for electrolysis to be integrated (tobe a laminate) to thereby facilitate renewing of the electrode. Theliquid between the membrane and the electrode for electrolysis or themetal porous plate or metal plate (feed conductor) and the electrode forelectrolysis may be present in an amount such that the both adhere toeach other by the surface tension. As a result, after the laminate isplaced in an electrolytic cell, the liquid, if mixed into theelectrolyte solution, does not affect electrolysis itself due to thesmall amount of the liquid.

From a practical viewpoint, a liquid having a surface tension of 20 mN/mto 80 mN/m, such as ethanol, ethylene glycol, and water, is preferablyused as the liquid. Particularly preferred is water or an alkalineaqueous solution prepared by dissolving caustic soda, potassiumhydroxide, lithium hydroxide, sodium hydrogen carbonate, potassiumhydrogen carbonate, sodium carbonate, potassium carbonate, or the likein water. Alternatively, the surface tension can be adjusted by allowingthese liquids to contain a surfactant. When a surfactant is contained,the adhesion between the membrane and the electrode for electrolysis orthe metal plate and the electrode for electrolysis varies to enable thehandling property to be adjusted. The surfactant is not particularlylimited, and both ionic surfactants and nonionic surfactants may beused.

The electrode for electrolysis of the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is not particularly limited, but is preferably 300 μmor less, more preferably 205 μm or less, further preferably 155 μm orless, further preferably 135 μm or less, further more preferably 125 μmor less, still more preferably 120 μm or less, even still morepreferably 100 μm or less from the viewpoint of enabling a good handlingproperty to be provided, having a good adhesive force to a membrane suchas an ion exchange membrane and a microporous membrane, a degradedelectrode, and a feed conductor having no catalyst coating, beingcapable of being suitably rolled in a roll and satisfactorily folded,and facilitating handling in a large size (e.g., a size of 1.5 m×2.5 m),and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

The proportion measured by the following method (2) of the electrode forelectrolysis of the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode, and a feed conductorhaving no catalyst coating, and further preferably 95% or more from theviewpoint of further facilitating handling in a large size (e.g., a sizeof 1.5 m×2.5 m). The upper limit value is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode forelectrolysis (130 mm square) are laminated in this order. The laminateis placed on a curved surface of a polyethylene pipe (outer diameter:280 mm) such that the sample of electrode for electrolysis in thislaminate is positioned outside under conditions of a temperature of23±2° C. and a relative humidity of 30±5%, the laminate and the pipe aresufficiently immersed in pure water, excess water deposited on a surfaceof the laminate and the pipe is removed, and one minute after thisremoval, then the proportion (%) of an area of a portion in which theion exchange membrane (170 mm square) is in close contact with thesample of electrode for electrolysis is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis of the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, and a feed conductor havingno catalyst coating and being capable of being suitably rolled in a rolland satisfactorily folded, and is further preferably 90% or more fromthe viewpoint of further facilitating handling in a large size (e.g., asize of 1.5 m×2.5 m). The upper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode forelectrolysis (130 mm square) are laminated in this order. The laminateis placed on a curved surface of a polyethylene pipe (outer diameter:145 mm) such that the sample of electrode for electrolysis in thislaminate is positioned outside under conditions of a temperature of23±2° C. and a relative humidity of 30±5%, the laminate and the pipe aresufficiently immersed in pure water, excess water deposited on a surfaceof the laminate and the pipe is removed, and one minute after thisremoval, then the proportion (%) of an area of a portion in which theion exchange membrane (170 mm square) is in close contact with thesample of electrode for electrolysis is measured.

The electrode for electrolysis of the present embodiment preferably has,but is not particularly limited to, a porous structure and an openingratio or void ratio of 5 to 90% or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode, and a feed conductor having no catalyst coating, andpreventing accumulation of gas to be generated during electrolysis. Theopening ratio is more preferably 10 to 80% or less, further preferably20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V was calculatedfrom the values of the gauge thickness, width, and length of theelectrode, and further, a weight W was measured to thereby calculate anopening ratio A by the following formula.

A=(1=(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio is appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

The value obtained by measurement by the following method (A) of theelectrode for electrolysis in the present embodiment is preferably 40 mmor less, more preferably 29 mm or less, further preferably 10 mm orless, further more preferably 6.5 mm or less from the viewpoint of thehandling property. The specific measuring method is as described inExamples.

[Method (A)]

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, a sample obtained by laminating the ion exchange membrane and theelectrode for electrolysis is wound around and fixed onto a curvedsurface of a core material being made of polyvinyl chloride and havingan outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter,when the electrode for electrolysis is separated from the sample andplaced on a flat plate, heights in a vertical direction at both edges ofthe electrode for electrolysis L₁ and L₂ are measured, and an averagevalue thereof is used as a measurement value.

In the electrode for electrolysis in the present embodiment, theventilation resistance is preferably 24 kPa·s/m or less when theelectrode for electrolysis has a size of 50 mm×50 mm, the ventilationresistance being measured under the conditions of the temperature of 24°C., the relative humidity of 32%, a piston speed of 0.2 cm/s, and aventilation volume of 0.4 cc/cm²/s (hereinbelow, also referred to as“measurement condition 1”) (hereinbelow, also referred to as“ventilation resistance 1”). A larger ventilation resistance means thatair is unlikely to flow and refers to a state of a high density. In thisstate, the product from electrolysis remains in the electrode and thereaction substrate is more unlikely to diffuse inside the electrode, andthus, the electrolytic performance (such as voltage) tends todeteriorate. The concentration on the membrane surface tends toincrease. Specifically, the caustic concentration increases on thecathode surface, and the supply of brine tends to decrease on the anodesurface. As a result, the product accumulates at a high concentration onthe interface at which the membrane is in contact with the electrode.This accumulation leads to damage of the membrane and tends to also leadto increase in the voltage and image of the membrane on the cathodesurface and damage of the membrane on the anode surface. In the presentembodiment, in order to prevent these defects, the ventilationresistance is preferably set at 24 kPa·s/m or less. From a similarviewpoint as above, the ventilation resistance is more preferably lessthan 0.19 kPa·s/m, further preferably 0.15 kPa·s/m or less, further morepreferably 0.07 kPa·s/m or less.

In the present embodiment, when the ventilation resistance is largerthan a certain value, NaOH generated in the electrode tends toaccumulate on the interface between the electrode and the membrane toresult in a high concentration in the case of the cathode, and thesupply of brine tends to decrease to cause the brine concentration to belower in the case of the anode. In order to prevent damage to themembrane that may be caused by such accumulation, the ventilationresistance is preferably less than 0.19 kPa·s/m, more preferably 0.15kPa·s/m or less, further preferably 0.07 kPa·s/m or less.

In contrast, when the ventilation resistance is low, the area of theelectrode is reduced and the electrolysis area is reduced. Thus, theelectrolytic performance (such as voltage) tends to deteriorate. Whenthe ventilation resistance is zero, the feed conductor functions as theelectrode because no electrode for electrolysis is provided, and theelectrolytic performance (such as voltage) tends to markedlydeteriorate. From this viewpoint, a preferable lower limit valueidentified as the ventilation resistance 1 is not particularly limited,but is preferably more than 0 kPa·s/m, more preferably 0.0001 kPa·s/m ormore, further preferably 0.001 kPa·s/m or more.

When the ventilation resistance 1 is 0.07 kPa·s/m or less, a sufficientmeasurement accuracy may not be achieved because of the measurementmethod therefor. From this viewpoint, it is also possible to evaluate anelectrode for electrolysis having a ventilation resistance 1 of 0.07kPa·s/m or less by means of a ventilation resistance (hereinbelow, alsoreferred to as “ventilation resistance 2”) obtained by the followingmeasurement method (hereinbelow, also referred to as “measurementcondition 2”). That is, the ventilation resistance 2 is a ventilationresistance measured, when the electrode for electrolysis has a size of50 mm×50 mm, under conditions of the temperature of 24° C., the relativehumidity of 32%, a piston speed of cm/s, and a ventilation volume of 4cc/cm²/s.

The specific methods for measuring the ventilation resistances 1 and 2are described in Examples.

The ventilation resistances 1 and 2 can be within the range describedabove by appropriately adjusting an opening ratio, thickness of theelectrode, and the like, for example. More specifically, for example,when the thickness is constant, a higher opening ratio tends to lead tosmaller ventilation resistances 1 and 2, and a lower opening ratio tendsto lead to larger ventilation resistances 1 and 2.

Hereinbelow, one aspect of the electrode for electrolysis of the presentembodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 1, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode. One first layer 20 may belaminated only on one surface of the substrate for electrode forelectrolysis 10.

Also shown in FIG. 1, the surfaces of the first layers 20 may be coveredwith second layers 30. The entire first layers 20 are preferably coveredby the second layers 30. Alternatively, one second layer 30 may belaminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, and further, valve metals includingtitanium can be used, although not limited thereto. At least one elementselected from nickel (Ni) and titanium (Ti) is preferably included. Thatis, the substrate for electrode for electrolysis preferably includes atleast one element selected from nickel (Ni) and titanium (Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed by eletroforming,so-called woven mesh produced by knitting metal lines, and the like canbe used. Among these, a perforated metal or expanded metal ispreferable. Electroforming is a technique for producing a metal thinfilm having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, foamed metal,metal nonwoven fabric, expanded metal, perforated metal, metal porousfoil, and the like can be used, although not limited thereto.

Examples of the substrate for electrode for electrolysis 10 include ametal foil, a wire mesh, a metal nonwoven fabric, a perforated metal, anexpanded metal, or a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil preferably further subjected to a plating treatment byuse of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on the surface thereof.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina grid, or the like on thesurface of the substrate for electrode for electrolysis followed by anacid treatment to increase the surface area thereof, in order to improvethe adhesion to a catalyst layer with which the surface is covered. Itis preferable to give a plating treatment by use of the same element asthe substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 5 μm.

Next, a case where the electrode for electrolysis of the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 1, a first layer 20 as a catalyst layer contains at least one ofruthenium oxides, iridium oxides, and titanium oxides. Examples of theruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol of the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thicknesspreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis of the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Ph, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The durabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals. The first layer 30 mayor may not contain at least one of platinum group metals, platinum groupmetal oxides, platinum group metal hydroxides, and alloys containing aplatinum group metal. Examples of a preferable combination of elementscontained in the second layer include the combinations enumerated forthe first layer. The combination of the first layer and the second layermay be a combination in which the compositions are the same and thecomposition ratios are different or may be a combination of differentcompositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thicknesspreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis was measured in the same manner as thethickness of the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking of a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. Among these, the pyrolysismethod, plating method, and ion plating method are preferable becausethe catalyst layer can be formed while deformation of the substrate forelectrode for electrolysis is prevented. When the viewpoint ofproductivity is added, the plating method and pyrolysis method arefurther preferable. The production method of the present embodiment asmentioned can achieve a high productivity of the electrode forelectrolysis 100. Specifically, in the pyrolysis method, a catalystlayer is formed on the substrate for electrode for electrolysis by anapplication step of applying a coating liquid containing a catalyst, adrying step of drying the coating liquid, and a pyrolysis step ofperforming pyrolysis. Pyrolysis herein means that a metal salt which isto be a precursor is decomposed by heating into a metal or metal oxideand a gaseous substance. The decomposition product depends on the metalspecies to be used, type of the salt, and the atmosphere under whichpyrolysis is performed, and many metals tend to form oxides in anoxidizing atmosphere. In an industrial process of producing an electrodefor electrolysis, pyrolysis is usually performed in air, and a metaloxide or a metal hydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coating issubstantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first. coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer of Anode)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 is obtained by applying a solution in which metalsalts of various combination are dissolved (first coating liquid) ontothe substrate for electrode for electrolysis and then pyrolyzing(baking) the coating liquid in the presence of oxygen. The content ofthe metal in the first coating liquid is substantially equivalent tothat in the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as ethanol and butanol can be used. As the solvent, water or amixed solvent of water and an alcohol is preferable. The total metalconcentration in the first coating liquid in which the metal salts aredissolved is, but is not particularly limited to, preferably in therange of 10 to 150 g/L in association with the thickness of the coatingfilm to be formed by a single coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then further baked fora long period as required, heating in the range of 350° C. to 650° C.for one minute to 90 minutes can further improve the stability of thefirst layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, with no solution applied thereon, in therange of 300° C. to 580° C. for one minute to 60 minutes.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by ion plating.

An example includes a method in which the substrate is fixed in achamber and the metal ruthenium target is irradiated with an electronbeam. Evaporated metal ruthenium particles are positively charged inplasma in the chamber to deposit on the substrate negatively charged.The plasma atmosphere is argon and oxygen, and ruthenium deposits asruthenium oxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

The electrode for electrolysis of the present embodiment can beintegrated with a membrane such as an ion exchange membrane and amacroporous membrane and used. Thus, the electrode can be used as amembrane-integrated electrode. Then, the substituting work for thecathode and anode on renewing the electrode is eliminated, and the workefficiency is markedly improved.

The electrode for electrolysis of the present embodiment forms alaminate with a membrane such as an ion exchange membrane and amicroporous membrane to be an integrated piece of the membrane and theelectrode, and then can make the electrolytic performance comparable toor higher than those of a new electrode. The membrane is notparticularly limited as long as the membrane can be laminated with theelectrode, and will be described in detail below.

[Ion Exchange Membrane]

The ion exchange membrane has a membrane body containing a hydrocarbonpolymer or fluorine-containing polymer having an ion exchange group anda coating layer provided on at least one surface of the membrane body.The coating layer contains inorganic material particles and a binder,and the specific surface area of the coating layer is 0.1 to 10 m²/g. Inthe ion exchange membrane having such a structure, the influence of gasgenerated during electrolysis on electrolytic performance is small, andstable electrolytic performance can be exhibited.

The ion exchange membrane described above includes either one of asulfonic acid layer having an ion exchange group derived from a sulfogroup (a group represented by —SO₃ ⁻, hereinbelow also referred to as a“sulfonic acid group”) or a carboxylic acid layer having an ion exchangegroup derived from a carboxyl group (a group represented by —CO₂ ⁻,hereinbelow also referred to as a “carboxylic acid group”). From theviewpoint of strength and dimension stability, reinforcement corematerials are preferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 2 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containingpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 includes a sulfonicacid layer 3 and a carboxylic acid layer 2, and reinforcement corematerials 4 enhance the strength and dimension stability. The ionexchange membrane 1, including the sulfonic acid layer 3 and thecarboxylic acid layer 2, is suitably used as an ion exchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 2.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)_(s)—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time of hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane 1, a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer 2 is located on the cathodeside of the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably high anion exclusion propertieseven if it has a small membrane thickness. The anion exclusionproperties here refer to the property of trying to hinder intrusion andpermeation of anions into and through the ion exchange membrane 1. Inorder to raise the anion exclusion properties, it is effective todispose a carboxylic acid layer having a small ion exchange capacity tothe sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F asthe monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane has a coating layer on at least one surface ofthe membrane body. As shown in FIG. 2, in the ion exchange membrane 1,coating layers 11 a and 11 b are formed on both the surfaces of themembrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides of Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durability, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurities suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contraction of the ion exchange membrane can be controlledin the desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, alkalis, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) is preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion change membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area of a surface through which substances such asions (an electrolyte solution and cations contained therein (e.g.,sodium ions)) can pass (B) to the area of either one surface of themembrane body (A) (B/A). The total area of the surface through whichsubstances such as ions can pass (B) can refer to the total areas ofregions in which in the ion exchange membrane, cations, an electrolyticsolution, and the like are not blocked by the reinforcement corematerials and the like contained in the ion exchange membrane.

FIG. 3 illustrates a schematic view for explaining the aperture ratio ofreinforcement core materials constituting the ion exchange membrane.FIG. 3, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapeof sacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above flourine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step (4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include(i) a method in which a fluorine-containing polymer having a carboxylicacid group precursor (e.g., carboxylate functional group) (hereinafter,a layer comprising the same is referred to as the first layer) locatedon the cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property of sufficiently retaining the mechanicalstrength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration or the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtainedthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DSMO).

The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 4(a) and (b) are schematic viewsfor explaining a method for forming the continuous holes of the ionexchange membrane.

FIGS. 4(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 4(a) exemplifies the plain-woven reinforcing material in which thereinforcement yarns 52 and sacrifice yarns 504 a are interwoven alongboth the longitudinal direction and the lateral direction in the paper,and the arrangement of the reinforcement yarns 52 and the sacrificeyarns 504 a in the reinforcing material may be varied as required.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counter the ion exchange group by H+ (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but thin coating liquidis preferable. This enables uniform application onto the surface of theion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating thereby providean ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example, and ispreferably 30 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

[Laminate]

The laminate of the present embodiment comprises the electrode forelectrolysis of the present embodiment, and a membrane or feed conductorin contact with the electrode for electrolysis. The laminate of thepresent embodiment, as configured as described above, can improve thework efficiency during electrode renewing in an electrolyzer andfurther, can exhibit excellent electrolytic performance also afterrenewing.

That is, according to the laminate of the present embodiment, onrenewing the electrode, the electrode can be renewed by a work as simpleas renewing the membrane, without a complicated work such as strippingoff the electrode fixed on the electrolytic cell, and thus, the workefficiency is markedly improved.

Further, according to the laminate or the present invention, it ispossible to maintain the electrolytic performance comparable to those ofa new electrode or improve the electrolytic performance. Even in thecase where only a feed conductor is placed in a new electrolytic cell(i.e., an electrode including no catalyst layer placed), only attachingthe electrode for electrolysis of the present embodiment to the feedconductor enables the electrode to function. Thus, it may be alsopossible to markedly reduce or eliminate catalyst coating.

The laminate of the present embodiment can be stored or transported tocustomers in a state where the laminate is wound around a vinyl chloridepipe or the like (in a rolled state or the like), making handlingmarkedly easier.

As the feed conductor of the present embodiment, various substratesmentioned below such as a degraded electrode (i.e., the existingelectrode) and an electrode having no catalyst coating can be employed.

In the laminate of the present embodiment, the force applied per unitmass·unit area of the electrode for electrolysis on the membrane or feedconductor is preferably 0.08 N/(mg·cm²) or more, more preferably 0.1N/(mg·cm²) or more, further preferably 0.14 N/(mg·cm²) or more, andfurther more preferably, from the viewpoint of further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m), is 0.2N/(mg·cm²) or more. The upper limit value is not particularly limited,but is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless. The upper limit value is ever still more preferably 1.1 N/mg·cm²or less, further still more preferably 1.10 N/mg·cm² or less,particularly preferably 1.0 N/mg·cm² or less, especially preferably 1.00N/mg·cm² or less.

[Wound Body]

The wound body of the present embodiment includes the electrode forelectrolysis of the present embodiment or the laminate of the presentembodiment. That is, the wound body of the present embodiment isobtained by winding the electrode for electrolysis of the presentembodiment or the laminate of the present embodiment. Downsizing theelectrode for electrolysis of the present embodiment or the laminate ofthe present embodiment by winding, as the wound body of the presentembodiment, can further improve the handling property.

[Electrolyzer]

The electrolyzer of the present embodiment includes the electrode forelectrolysis of the present embodiment. Hereinafter, the case ofperforming common salt electrolysis by using an ion exchange membrane asthe membrane is taken as an example, and one embodiment of theelectrolyzer will be described in detail.

[Electrolytic Cell]

FIG. 5 illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell 1 has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 9, and the cathode 21 and the reverse current absorbinglayer 18 b are electrically connected. The cathode chamber 20 furtherhas a collector 23, a support 24 supporting the collector, and a metalelastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer may be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support 24, the support 24 and the collector 23, and the collector23 and the metal elastic body 22 are each directly attached and thecathode 21 is laminated on the metal elastic body 22. Examples of amethod for directly attaching these constituent members to one anotherinclude welding and the like. Alternatively, the reverse currentabsorber 18, the cathode 21, and the collector 23 may be collectivelyreferred to as a cathode structure 40.

FIG. 6 illustrates a cross-sectional view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 7 shows an electrolyzer 4.FIG. 8 shows a step of assembling the electrolyzer 4. As shown in FIG.6, an electrolytic cell 1, a cation exchange membrane 2, and anelectrolytic cell 1 are arranged in series in the order mentioned. Anion exchange membrane 2 is arranged between the anode chamber of oneelectrolytic cell 1 among the two electrolytic cells that are adjacentin the electrolyzer and the cathode chamber of the other electrolyticcell 1. That is, the anode chamber 10 of the electrolytic cell 1 and thecathode chamber 20 of the electrolytic cell 1 adjacent thereto isseparated by the cation exchange membrane 2. As shown in FIG. 7, theelectrolyzer 4 is composed of a plurality of electrolytic cells 1connected in series via the ion exchange membrane 2. That is, theelectrolyzer 4 is a bipolar electrolyzer comprising the plurality ofelectrolytic cells 1 arranged in series and ion exchange membranes 2each arranged between adjacent electrolytic cells 1. As shown in FIG. 8,the electrolyzer 4 is assembled by arranging the plurality ofelectrolytic cells 1 in series via the ion exchange membrane 2 andcoupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That is, the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine is electrolyzed, chlorine gas is generated onthe side of the anode 11, and sodium hydroxide (solute) and hydrogen gasare generated on the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Whenthe electrode for electrolysis of the present embodiment is inserted tothe anode side, 11 serves as the anode feed conductor. When theelectrode for electrolysis of the present embodiment is not inserted tothe anode side, 11 serves as the anode. The anode chamber 10 has ananode-side electrolyte solution supply unit that supplies an electrolytesolution to the anode chamber 10, a baffle plate that is arranged abovethe anode-side electrolyte solution supply unit so as to besubstantially parallel or oblique to the partition wall 30, and ananode-side gas liquid separation unit arranged above the baffle plate toseparate gas from the electrolyte solution including the gas mixed.

(Anode)

When the electrode for electrolysis of the present embodiment is notinserted to the anode side, the anode 11 is provided in the frame of theanode chamber 10. As the anode 11, a metal electrode such as so-calledDSA(R) can be used. DSA is an electrode including a titanium substrateof which surface is covered with an oxide comprising ruthenium, iridium,and titanium as component.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis of the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA having athinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 5,and below means the lower direction in the electrolytic cell 1 in FIG.5.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 of the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 5, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis of thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis of thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis of the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20. The cathode 21 preferably has a nickel substrateand a catalyst layer that covers the nickel substrate. Examples of thecomponents of the catalyst layer on the nickel substrate include metalssuch as Pu, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi,La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, andoxides and hydroxides of the metals. Examples of the method for formingthe catalyst layer include plating, alloy plating, dispersion compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. The cathode 21 may be subjected to areduction treatment, as required. As the substrate of the cathode 21,nickel, nickel alloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis of the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. As the substrate of the cathode feedconductor 21, nickel, nickel alloys, and nickel-plated iron or stainlessmay be used.

As the feed conductor 21, nickel, nickel alloys, and nickel-plated ironor stainless, having no catalyst coating may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electrolytic cells 1 connected in series. Lowering of thevoltage enables the power consumption to be reduced. With the metalelastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis according to the present invention is placed in theelectrolytic cell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning, mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantial perpendicular to the partitionwall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane 2 (see FIGS. 5 and 6). These gaskets can impart airtightness toconnecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced gas and be usable for long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 6), each electrolytic cell 1 onto which the gasketis attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

(Ion Exchange Membrane 2)

The ion exchange membrane 2 is as described in the section of the ionexchange membrane described above.

(Water Electrolysis)

The electrolyzer of the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

Second Embodiment

Here, a second embodiment of the present invention will be described indetail with reference to FIGS. 22 to 42.

[Laminate]

A laminate of the second embodiment (hereinafter, in the section of<Second embodiment>, simply referred to as “the present embodiment”)comprises an electrode for electrolysis and a membrane or feed conductorin contact with the electrode for electrolysis, wherein a force appliedper unit mass·unit area of the electrode for electrolysis on themembrane or feed conductor is less than 1.5 N/mg·cm². The laminate ofthe present embodiment, as configured as described above, can improvethe work efficiency during electrode renewing in an electrolyzer andfurther, can exhibit excellent electrolytic performance also afterrenewing.

That is, according to the laminate of the present embodiment, onrenewing the electrode, the electrode can be renewed by a work as simpleas renewing the membrane, without a complicated work such as strippingoff the existing electrode fixed on the electrolytic cell, and thus, thework efficiency is markedly improved.

Further, according to the laminate of the present invention, it ispossible to maintain or improve the electrolytic performance of a newelectrode. Thus, the electrode fixed on a conventional new electrolyticcell and serving as an anode and/or a cathode is only required to serveas a feed conductor. Thus, it may be also possible to markedly reduce oreliminate catalyst coating.

The laminate of the present embodiment can be stored or transported tocustomers in a state where the laminate is wound around a vinyl chloridepipe or the like (in a rolled state or the like), making handlingmarkedly easier.

As the feed conductor of the present embodiment, various substratesmentioned below such as a degraded electrode (i.e., the existingelectrode) and an electrode having no catalyst coating can be employed.

The laminate of the present embodiment may have partially a fixedportion as long as the laminate has the configuration described above.That is, in the case where the laminate of the present embodiment has afixed portion, a portion not having the fixing is subjected tomeasurement, and the resulting force applied per unit mass·unit area ofthe electrode for electrolysis should be less than 1.5 N/mg·cm².

[Electrode for Electrolysis]

The electrode for electrolysis of the present embodiment has a forceapplied per unit mass·unit area of less than 1.5 N/mg·cm², preferably1.2 N/mg·cm² or less, more preferably 1.20 N/mg·cm² or less from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a feed conductor (a degraded electrode and anelectrode having no catalyst coating), and the like. The force isfurther preferably 1.1 N/mg·cm² or less, further preferably 1.10N/mg·cm² or less, still more preferably 1.0 N/mg·cm² or less, even stillmore preferably 1.00 N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0.2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit area is preferably 48 mg/cm² or less, more preferably30 mg/cm² or less, further preferably 20 mg/cm² or less from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and economy, and furthermore is preferably 15 mg/cm²or less from the comprehensive viewpoint including handling property,adhesion, and economy. The lower limit value is not particularly limitedbut is of the order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as described in Examples, specifically. As for theforce applied, the value obtained by the measurement of the method (i)(also referred to as “the force applied (1)”) and the value obtained bythe measurement of the method (ii) (also referred to as “the forceapplied (2)”) may be the same or different, and either of the values isless than 1.5 N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode (130 mm square) are laminated in this order.After this laminate is sufficiently immersed in pure water, excess waterdeposited on the surface of the laminate is removed to obtain a samplefor measurement. The arithmetic average surface roughness (Pa) of thenickel plate after the blast treatment is 0.5 to 0.8 μm. The specificmethod for calculating the arithmetic average surface roughness (Ra) isas described in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method (i)is less than 1.5 N/mg·cm², preferably 1.2 N/mg·cm² or less, morepreferably 1.20 N/mg·cm² or less, further preferably 1.1 N/mg·cm² orless, further more preferably 1.10 N/mg·cm² of less, still morepreferably 1.0 N/mg·cm² of less, even still more preferably 1.00N/mg·cm² or less from the viewpoint of enabling a good handling propertyto be provided and having a good adhesive force to a membrane such as anion exchange membrane and a microporous membrane, a degraded electrode,and a feed conductor having no catalyst coating. The force is preferablymore than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²) or more,further preferably 0.1 N/(mg·cm²) or more from the viewpoint of furtherimproving the electrolytic performance, and furthermore, is further morepreferably 0.14 N/(mg·cm²), still more preferably 0.2 N/(mg·cm²) or morefrom the viewpoint of further facilitating handling in a large size(e.g., a size of 1.5 m×2.5 m).

When the electrode for electrolysis of the present embodiment satisfiesthe force applied (1), the electrode can be integrated with a membranesuch as an ion exchange membrane and a microporous membrane or a feedconductor, for example, and used (i.e., as a laminate). Thus, onrenewing the electrode, the substituting work for the cathode and anodefixed on the electrolytic cell by a method such as welding iseliminated, and the work efficiency is markedly improved. Additionally,by use of the electrode for electrolysis of the present embodiment as alaminate integrated with the ion exchange membrane, microporousmembrane, or feed conductor, it is possible to make the electrolyticperformance comparable to or higher than those of a new electrode.

On shipping a new electrolytic cell, an electrode fixed on anelectrolytic cell has been subjected to catalyst coating conventionally.Since only combination of an electrode having no catalyst coating withthe electrode for electrolysis of the present embodiment can allow theelectrode to function as an electrode, it is possible to markedly reduceor eliminate the production step and the amount of the catalyst forcatalyst coating. A conventional electrode of which catalyst coating ismarkedly reduced or eliminated can be electrically connected to theelectrode for electrolysis of the present embodiment and allowed toserve as a feed conductor for passage of an electric current.

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurement. Under conditionsof a temperature of 23±2° C. and a relative humidity of 30±5%, only thesample of electrode in this sample for measurement is raised in avertical direction at 10 mm/minute using a tensile and compressiontesting machine, and the load when the sample of electrode is raised by10 mm in a vertical direction is measured. This measurement is repeatedthree times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is less than 1.5 N/mg·cm², preferably 1.2 N/mg·cm² or less, morepreferably 1.20 N/mg·cm² or less, further preferably 1.1 N/mg·cm² orless, further more preferably 1.10 N/mg·cm² or less, still morepreferably 1.0 N/mg·cm² or less, even still more preferably 1.00N/mg·cm² or less from the viewpoint of enabling a good handling propertyto be provided and having a good adhesive force to a membrane such as anion exchange membrane and a microporous membrane, a degraded electrode,and a feed conductor having no catalyst coating. The force is preferablymore than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²) or more,further preferably 0.1 N/(mg·cm²) or more from the viewpoint of furtherimproving the electrolytic performance, and is further more preferably0.14 N/(mg·cm²) or more from the viewpoint of further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m).

The electrode for electrolysis of the present embodiment, if satisfiesthe force applied (2), can be stored or transported to customers in astate where the electrode is wound around a vinyl chloride pipe or thelike (in a rolled state or the like), making handling markedly easier.By attaching the electrode for electrolysis of the present embodiment toa degraded existing electrode to provide a laminate, it is possible tomake the electrolytic performance comparable to or higher than those ofa new electrode.

From the viewpoint that the electrode for electrolysis of the presentembodiment, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm less, further still morepreferably 135 μm or less. A thickness of 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

The electrode for electrolysis of the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 120 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, being capable of being suitably rolled in aroll and satisfactorily folded, and facilitating handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 μm, more preferably 15 μm.

In the present embodiment, a liquid is preferably interposed between themembrane such as an ion exchange membrane and a microporous membrane andthe electrode, or the metal porous plate or metal plate (i.e., feedconductor) such as a degraded existing electrode and electrode having nocatalyst coating and the electrode for electrolysis. As the liquid, anyliquid, such as water and organic solvents, can be used as long as theliquid generates a surface tension. The larger the surface tension ofthe liquid, the larger the force applied between the membrane and theelectrode for electrolysis or the metal porous plate or metal plate andthe electrode for electrolysis. Thus, a liquid having a larger surfacetension is preferred. Examples of the liquid include the following (thenumerical value in the parentheses is the surface tension of the liquidat 20° C.)

hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00 mN/m),ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and water (72.76mN/m).

A liquid having a large surface tension allows the membrane and theelectrode for electrolysis or the metal porous plate or metal plate(feed conductor) and the electrode for electrolysis to be integrated (tobe a laminate) to thereby facilitate renewing of the electrode. Theliquid between the membrane and the electrode for electrolysis or themetal porous plate or metal plate (feed conductor) and the electrode forelectrolysis may be present in an amount such that the both adhere toeach other by the surface tension. As a result, after the laminate isplaced in an electrolytic cell, the liquid, if mixed into theelectrolyte solution, does not affect electrolysis itself due to thesmall amount of the liquid.

From a practical viewpoint, a liquid having a surface tension of 24 mN/mto 80 mN/m, such as ethanol, ethylene glycol, and water, is preferablyused as the liquid. Particularly preferred is water or an alkalineaqueous solution prepared by dissolving caustic soda, potassiumhydroxide, lithium hydroxide, sodium hydrogen carbonate, potassiumhydrogen carbonate, sodium carbonate, potassium carbonate, or the likein water. Alternatively, the surface tension can be adjusted by allowingthese liquids to contain a surfactant. When a surfactant is contained,the adhesion between the membrane and the electrode for electrolysis orthe metal porous plate or metal plate (feed conductor) and the electrodefor electrolysis varies to enable the handling property to be adjusted.The surfactant is not particularly limited, and both ionic surfactantsand nonionic surfactants may be used.

The proportion measured by the following method (2) of the electrode forelectrolysis of the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint or further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis of the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The electrode for electrolysis of the present embodiment preferably hasa porous structure and an opening ratio or void ratio of 5 to 90% orless from the viewpoint of enabling a good handling property to beprovided, having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode (feedconductor), and an electrode (feed conductor) having no catalystcoating, and preventing accumulation of gas to be generated duringelectrolysis, although not particularly limited. The opening ratio ismore preferably 10 to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V was calculatedfrom the values of the gauge thickness, width, and length of theelectrode, and further, a weight W was measured to thereby calculate anopening ratio A by the following formula.

A=(1−(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio is appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

The value obtained by measurement by the following method (A) of theelectrode for electrolysis in the present embodiment is preferably 40 mmor less, more preferably 29 mm or less, further preferably 10 mm orless, further more preferably 6.5 mm or less from the viewpoint of thehandling property. The specific measuring method is as described inExamples.

[Method (A)]

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, a sample obtained by laminating the ion exchange membrane and theelectrode for electrolysis is wound around and fixed onto a curvedsurface of a core material being made of polyvinyl chloride and havingan outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter,when the electrode for electrolysis is separated from the sample andplaced on a flat plate, heights in a vertical direction at both edges ofthe electrode for electrolysis L₁ and L₂ are measured, and an averagevalue thereof is used as a measurement value.

In the electrode for electrolysis in the present embodiment, theventilation resistance is preferably 24 kPa·s/m or less when theelectrode for electrolysis has a size of 50 mm×50 mm, the ventilationresistance being measured under conditions of the temperature of 24° C.,the relative humidity of 32%, a piston speed of 0.2 cm/s, and aventilation volume of 0.4 cc/cm²/s (hereinbelow, also referred to as“measurement condition 1”) (hereinbelow, also referred to as“ventilation resistance 1”). A larger ventilation resistance means thatair is unlikely to flow and refers to a state of a high density. In thisstate, the product from electrolysis remains in the electrode and thereaction substrate is more unlikely to diffuse inside the electrode, andthus, the electrolytic performance (such as voltage) tends todeteriorate. The concentration on the membrane surface tends toincrease. Specifically, the caustic concentration increases on thecathode surface, and the supply of brine tends to decrease on the anodesurface. As a result, the product accumulates at a high concentration onthe interface at which the membrane is in contact with the electrode.This accumulation leads to damage of the membrane and tends to also leadto increase in the voltage and damage of the membrane on the cathodesurface and damage of the membrane on the anode surface. In the presentembodiment, in order to prevent these defects, the ventilationresistance is preferably set at 24kPa·s/m or less. From a similarviewpoint as above, the ventilation resistance is more preferably lessthan 0.19 kPa·s/m, further preferably 0.15 kPa·s/m or less, further morepreferably 0.07 kPa·s/m or less.

In the present embodiment, when the ventilation resistance is largerthan a certain value, NaOH generated in the electrode tends toaccumulate on the interface between the electrode and the membrane toresult in a high concentration in the case of the cathode, and thesupply of brine tends to decrease to cause the brine concentration to belower the case of the anode. In order to prevent damage to the membranethat may be caused by such accumulation, the ventilation resistance ispreferably less than 0.19 kPa·s/m, more preferably 0.15 kPa·s/m or less,further preferably 0.07 kPa·s/m or less.

In contrast, when the ventilation resistance is low, the area of theelectrode is reduced and the electrolysis area is reduced. Thus, theelectrolytic performance (such as voltage) tends to deteriorate. Whenthe ventilation resistance is zero, the feed conductor functions as theelectrode because no electrode for electrolysis is provided, and theelectrolytic performance (such as voltage) tends to markedlydeteriorate. From this viewpoint, a preferable lower limit valueidentified as the ventilation resistance 1 is not particularly limited,but is preferably more than 0 kPa·s/m, more preferably 0.0001 kPa·s/m ormore, further preferably 0.001 kPa·s/m or more.

When the ventilation resistance 1 is 0.07 kPa·s/m or less, a sufficientmeasurement accuracy may not be achieved because of the measurementmethod therefor. From this viewpoint, it is also possible to evaluate anelectrode for electrolysis having a ventilation resistance 1 of 0.07kPa·s/m or less by means of a ventilation resistance (hereinbelow, alsoreferred to as “ventilation resistance 2”) obtained by the followingmeasurement method (hereinbelow, also referred to as “measurementcondition 2”). That is, the ventilation resistance 2 is a ventilationresistance measured, when the electrode for electrolysis has a size of50 mm×50 mm, under conditions of the temperature of 24° C., the relativehumidity of 32%, a piston speed of 2 cm/s, and a ventilation volume of 4cc/cm²/s.

The specific methods for measuring the ventilation resistances 1 and 2are described in Examples.

The ventilation resistances 1 and 2 can be within the range describedabove by appropriately adjusting an opening ratio, thickness of theelectrode, and the like, for example. More specifically, for example,when the thickness is constant, a higher opening ratio tends to lead tosmaller ventilation resistances 1 and 2, and a lower opening ratio tendsto lead to larger ventilation resistances 1 and 2.

In the electrode for electrolysis of the present embodiment, asmentioned above, the force applied per unit mass·unit area of theelectrode for electrolysis on the membrane or feed conductor is lessthan 1.5 N/mg·cm². In this manner, the electrode for electrolysis of thepresent embodiment abuts with a moderate adhesive force on the membraneor feed conductor (e.g., the existing anode or cathode in theelectrolyzer) to thereby enable a laminate with the membrane or feedconductor to be constituted. That is, it is not necessary to cause themembrane or feed conductor to firmly adhere to the electrode forelectrolysis by a complicated method such as thermal compression. Thelaminate is formed only by a relatively weak force, for example, asurface tension derived from moisture contained in the membrane such asan ion exchange membrane and a microporous membrane, and thus, alaminate of any scale can be easily constituted. Additionally, such alaminate exhibits excellent electrolytic performance. Thus, the laminateof the present embodiment is suitable for electrolysis applications, andcan be particularly preferably used for applications related to membersof electrolyzers and renewing the members.

Hereinbelow, one aspect of the electrode for electrolysis of the presentembodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 22, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also shown in FIG. 22, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis of the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 22, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol of the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis of the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium±lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium±samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The durabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, andLu, and oxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode for electrolysis, that is, the totalthickness of the substrate for electrode for electrolysis and thecatalyst layer is preferably 315 μm or less, more preferably 220 μm orless, further preferably 170 μm or less, further more preferably 150 μmor less, particularly preferably 1.45 μm or less, still more preferably140 μm or less, even still more preferably 138 μm or less, further stillmore preferably 135 μm or less in respect of the handling property ofthe electrode for electrolysis. A thickness of 135 μm or less canprovide a good handling property. Further, from a similar viewpoint asabove, the thickness is preferably 130 μm or less, more preferably lessthan 130 μm, further preferably 115 μm or less, further more preferably65 μm or less. The lower limit value is not particular limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. The thickness of the electrodecan be determined by measurement with a digimatic thickness gauge(Mitutoyo Corporation, minimum scale 0.001 mm). The thickness of thesubstrate for electrode for electrolysis can be measured in the samemanner as in the case of the electrode for electrolysis. The thicknessof the catalyst layer can be determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode for electrolysis.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by for the first layer 20, preferably the second layer 30, onthe substrate for electrode for electrolysis by a method such as bakingor a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst layer is formedon the substrate for electrode for electrolysis by an application stepof applying a coating liquid containing a catalyst, a drying step ofdrying the coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysis isperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may he chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable 5 to 20minutes more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 obtained by applying a solution in which metal saltsof various combination are dissolved (first coating liquid) onto thesubstrate for electrode for electrolysis and then pyrolyzing (baking)the coating liquid in the presence of oxygen. The content of the metalin the first coating liquid is substantially equivalent to that in thefirst layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and the further post-bakedfor a long period as required can further improve the stability of thefirst layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating.

An example includes a method in which the substrate is fixed in achamber and the metal ruthenium target is irradiated with an electronbeam. Evaporated metal ruthenium particles are positively charged inplasma in the chamber to deposit on the substrate negatively charged.The plasma atmosphere is argon and oxygen, and ruthenium deposits asruthenium oxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

The electrode for electrolysis of the present embodiment can beintegrated with a membrane such as an exchange membrane and amicroporous membrane and used. Thus, the electrode can be used as amembrane-integrated electrode. Then, the substituting work for thecathode and anode on renewing the electrode is eliminated, and the workefficiency markedly improved.

The electrode integrated with the membrane such as an ion exchangemembrane and a microporous membrane can make the electrolyticperformance comparable to or higher than those of a new electrode.

Hereinafter, the ion exchange membrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane has a membrane body containing a hydrocarbonpolymer or fluorine-containing polymer having an ion exchange group anda coating layer provided on at least one surface of the membrane body.The coating layer contains inorganic material particles and a binder,and the specific surface area of the coating layer is 0.1 to 10 m²/g. Inthe ion exchange membrane having such a structure, the influence of gasgenerated during electrolysis on electrolytic performance is small, andstable electrolytic performance can be exhibited.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO₃ ⁻, hereinbelow also referred to as a “sulfonicacid group”) or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂ ⁻,hereinbelow also referred to as a “carboxylic acid group”). From theviewpoint of strength and dimension stability, reinforcement corematerials are preferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 23 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by —SO₃ ⁻, hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group (a group represented by—CO₂—, hereinbelow also referred to as a “carboxylic acid group”), andthe reinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane 1, as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 23.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing, polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include compounds having afunctional group convertible into a carboxylic acid-type ion exchangegroup (carboxylic acid group). Examples of the vinyl compounds having afunctional group convertible into a carboxy acid group include monomersrepresented by CF₂═CF(OCF₂CYF)_(s)—O(CZF)_(t)—COOR, wherein s representsan integer of 0 to 2, t represents an integer of 1 to 12, Y and Z eachindependently represent F or CF₃, and R represents a lower alkyl group(a lower alkyl group is an alkyl group having 1 to 3 carbon atoms, forexample).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time of hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the target fluorinecontaining polymer can be obtained also by separately preparing acopolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0. to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer 2 is located on the cathodeside of the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxyl acid layer 2,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃as the monomer of the second group.

(Coating Layer)

The ion exchange membrane has a coating layer on at least one surface ofthe membrane body. As shown in FIG. 23, in the ion exchange membrane 1,coating layers 11 a and 11 b are formed on both the surfaces of themembrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material articles can be 2 μmor less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a partcle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides of Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durability, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurities suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing, polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing, polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperaties on the surface thereof, the distribution densityof the coating, layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contraction of the ion exchange membrane can be controlledin the desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, alkalis, etc., and a fiber comprising afluorine-containing polymer preferable because long-term heat resistanceand chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) is preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred, to as MDyarns, and yarns woven along the TD are referred to as ID yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the ID. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area of a surface through which substances such asions (an electrolyte solution and cations contained therein (e.g.,sodium ions)) can pass (B) to the area of either one surface of themembrane body (A) (B/A). The total area of the surface through whichsubstances such as ions can pass (B) can refer to the total areas ofregions in which in the ion exchange membrane, cations, an electrolyticsolution, and the like are not blocked by the reinforcement corematerials and the like contained in the ion exchange membrane.

FIG. 24 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 24, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous boles refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapeof sacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method, for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step (4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step),

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method or forming a membrane body include amethod in which a fluorine-containing polymer having a carboxylic acidgroup precursor (e.g., carboxylate functional group) (hereinafter, alayer comprising the same is referred to as the first layer) located onthe cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer her en contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property of sufficiently retaining the mechanicalstrength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that is, projections, on the surface side composed of thesulfonic acid layer. As a method, for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains NON of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 25(a) and (b) are schematic viewsfor explaining a method for forming the continuous holes of the ionexchange membrane.

FIGS. 25(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 25(a) exemplifies the plain-woven reinforcing material in which thereinforcement yarns 52 and sacrifice yarns 504 a are interwoven alongboth the longitudinal direction and the lateral direction in the paper,and the arrangement of the reinforcement yarns 52 and the sacrificeyarns 504 a in the reinforcing material may be varied as required.

(6) Application step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counterion of the ion exchange group by H+ (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example, and ispreferably 30 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

The reason why the laminate with the membrane of the present embodimentdevelops excellent electrolytic performance is presumed as follows. Whenthe membrane and the electrode firmly adhere to each other by a methodsuch as thermal compression, which is a conventional technique, theelectrode sinks into the membrane to thereby physically adhere thereto.This adhesion portion inhibits sodium ions from migrating in themembrane to thereby markedly raise the voltage. Meanwhile, inhibition ofmigration of sodium ions in the membrane, which has been a problem inthe conventional art, is eliminated by allowing the electrode forelectrolysis to abut with a moderate adhesive force on the membrane orfeed conductor, as in the present embodiment. According to theforegoing, when the membrane or feed conductor abuts on the electrodefor electrolysis with a moderate adhesive force, the membrane or feedconductor and the electrode for electrolysis, despite of being anintegrated piece, can develop excellent electrolytic performance.

[Wound Body]

The wound body of the present embodiment includes the laminate of thepresent embodiment. That is, the wound body of the present embodiment isobtained by winding the laminate of the present embodiment. Downsizingthe laminate of the present embodiment by winding, like the wound bodyof the present embodiment, can further improve the handling property.

[Electrolyzer]

The electrolyzer of the present embodiment includes the laminate of thepresent embodiment. Hereinafter, the case of performing common saltelectrolysis by using an ion exchange membrane as the membrane is takenas an example, and one embodiment of the electrolyzer will be describedin detail.

[Electrolytic Cell]

FIG. 26 illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell 1 has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 30, and the cathode 1 and the reverse current absorbinglayer 18 b are electrically connected. The cathode chamber 20 furtherhas a collector 23, a support 24 supporting the collector, and a metalelastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer may be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support 24, the support 24 and the collector 23, and the collector23 and the metal elastic body 22 are each directly attached and thecathode 21 is laminated on the metal elastic body 22. Examples of amethod for directly attaching these constituent members to one anotherinclude welding and the like. Alternatively, the reverse currentabsorber 18, the cathode 21, and the collector 23 may be collectivelyreferred to as a cathode structure 40.

FIG. 27 illustrates a cross-sectional view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 28 shows an electrolyzer4. FIG. 29 shows a step of assembling the electrolyzer 4. As shown inFIG. 27, an electrolytic cell 1, a cation exchange membrane 2, and anelectrolytic cell 1 are arranged in series in the order mentioned. Anion exchange membrane 2 is arranged between the anode chamber of oneelectrolytic cell 1 among the two electrolytic cells that are adjacentin the electrolyzer and the cathode chamber of the other electrolyticcell 1. That is, the anode chamber 10 of the electrolytic cell 1 and thecathode chamber 20 of the electrolytic cell 1 adjacent thereto isseparated by the cation exchange membrane 2. As shown in FIG. 28, theelectrolyzer 4 is composed of a plurality of electrolytic cells 1connected in series via the ion exchange membrane 2. That is, theelectrolyzer 4 is a bipolar electrolyzer comprising the plurality ofelectrolytic cells 1 arranged in series and ion exchange membranes 2each arranged between adjacent electrolytic cells 1. As shown in FIG.29, the electrolyzer 4 is assembled by arranging the plurality ofelectrolytic cells 1 in series via the ion exchange membrane 2 andcoupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current during,electrolysis flows from the side or the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell throughthe ion exchange membrane to the cathode chamber 20 of the adjacentelectrolytic cell 1. Thus, the electric current during electrolysisflows in the direction in which the electrolytic cells 1 are coupled inseries. That is, the electric current flows, through the cation exchangemembrane 2, from the anode chamber 10 toward the cathode chamber 20. Asthe brine is electrolyzed, chlorine gas is generated on the side of theanode 11, and sodium hydroxide (solute) and hydrogen gas are generatedon the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Whenthe electrode for electrolysis of the present embodiment is inserted tothe anode side, 11 serves as the anode feed conductor. When theelectrode for electrolysis of the present embodiment is not inserted tothe anode side, 11 serves as the anode. The anode chamber 10 has ananode side electrolyte solution supply unit that supplies an electrolytesolution to the anode chamber 10, a baffle plate that is arranged abovethe anode-side electrolyte solution supply unit so as to besubstantially parallel or oblique to the partition wall 30, and ananode-side gas liquid separation unit arranged above the baffle plate toseparate gas from the electrolyte solution including the gas mixed.

(Anode)

When the electrode for electrolysis of the present embodiment is notinserted to the anode side, the anode 11 is provided in the frame of theanode chamber 10. As the anode 11, a metal electrode such as so-calledDSA(R) can be used. DSA is an electrode including a titanium substrateof which surface is covered with an oxide comprising ruthenium, iridium,and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis of the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA having athinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 26,and below means the lower direction in the electrolytic cell 1 in FIG.26.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 of the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 26, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding, a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis of thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed, conductor. When the electrode for electrolysis of thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis of the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20. The cathode 21 preferably has a nickel substrateand a catalyst layer that covers the nickel substrate. Examples of thecomponents of the catalyst layer on the nickel substrate include metalssuch as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi,La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, andoxides and hydroxides of the metals. Examples of the method for formingthe catalyst layer include platinu, alloy plating, dispersion/compositeplating CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. The cathode 21 may be subjected to areduction treatment, as required. As the substrate of the cathode 21,nickel, nickel alloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis of the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. Alternatively, nickel, nickelalloys, and nickel-plated iron or stainless, having no catalyst coating,may be used. As the substrate of the cathode feed conductor 21, nickel,nickel alloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entire across the pluralityof electrolytic cells 1 connected in series. Lowering of the voltageenables the power consumption to be reduced. With the metal elastic body22 placed, the pressing pressure caused by the metal elastic body 22enables the electrode for electrolysis to be stably maintained in placewhen the laminate including the electrode for electrolysis according tothe present embodiment is placed in the electrolytic cell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantially perpendicular to thepartition wall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane 2 (See FIGS. 26 and 27). These gaskets can impart airtightnessto connecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced as and be usable for long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 27), each electrolytic cell 1 onto which the gasketis attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

(Ion Exchange Membrane)

The ion exchange membrane 2 is as described in the section of the ionexchange membrane described above.

(Water Electrolysis)

The electrolyzer of the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

(Application of Laminate)

The laminate of the present embodiment can improve the work efficiencyduring electrode renewing in an electrolyzer and further, can exhibitexcellent electrolytic performance also after renewing as mentionedabove. In other words, the laminate of the present embodiment can besuitably used as a laminate for replacement of a member of anelectrolyzer. A laminate to be used in such an application isspecifically referred to as a “membrane electrode assembly”.

(Package)

The laminate of the present embodiment is preferably transported or thelike while enclosed in a packaging material. That is, the package of thepresent embodiment comprises the laminate of the present embodiment anda packaging material that packages the laminate. The package of thepresent embodiment, configured as described above, can prevent adhesionof stain and damage that may occur during transport or the like of thelaminate of the present embodiment. When used for member replacement ofthe electrolyzer, the laminate is particularly preferably transported orthe like as the package of the present embodiment. As the packagingmaterial of the present embodiment, which is not particularly limited,known various packaging materials can be employed. Alternatively, thepackage of the present embodiment can be produced by, for example, amethod including packaging the laminate of the present embodiment with aclean packaging material followed by encapsulation or the like, althoughnot limited thereto.

Third Embodiment

Here, a third embodiment of the present invention will be described indetail with reference to FIGS. 43 to 62.

[Laminate]

The laminate of the third embodiment (hereinafter, in the section of<Third embodiment>, simply referred to as “the present embodiment”) hasa membrane and an electrode for electrolysis fixed at least one regionof the surface of the “membrane ” (hereinafter, simply also referred toas a “fixed region”), and the proportion of the region on the surface ofthe membrane is more than 0% and less than 93%. The laminate of thepresent embodiment, as configured as described above, can improve thework efficiency during electrode renewing in an electrolyzer andfurther, can exhibit excellent electrolytic performance also afterrenewing.

That is, according to the laminate of the present embodiment, onrenewing the electrode, the electrode can be renewed by a work as simpleas renewing the membrane, without a complicated work such as strippingoff the existing electrode fixed on the electrolytic cell, and thus, thework efficiency is markedly improved.

Further, according to the laminate of the present embodiment, it ispossible to maintain the electrolytic performance of the existingelectrolytic cell comparable to those of a new electrode or improve theelectrolytic performance. Thus, the electrode fixed on the existingelectrolytic cell and serving as an anode and/or a cathode is onlyrequired to serve as a feed conductor. Thus, it may be also possible tomarkedly reduce or eliminate catalyst coating. The feed conductor hereinmeans a degraded electrode (i.e., the existing electrode), an electrodehaving no catalyst coating, and the like.

[Electrode for Electrolysis]

The electrode for electrolysis in the present embodiment is notparticularly limited as long as the electrode is an electrode to be usedfor electrolysis, and preferably has an area of the surface opposed tothe membrane of the electrode for electrolysis (corresponds to an areaof the conducting surface 32 mentioned below) of 0.01 m² or more. The“surface opposed to the membrane” means the surface on which themembrane is located of the surfaces possessed by the electrode forelectrolysis. That is, the surface opposed to the membrane in theelectrode for electrolysis also can be the surface that abuts on thesurface of the membrane. When the area of the surface opposed to themembrane in the electrode for electrolysis is 0.01 m² or more,sufficient productivity can be achieved, and especially when industrialelectrolysis is performed, sufficient productivity tends to be obtained.In this manner, from the viewpoint of achieving sufficient productivityand achieving practicality for a laminate to be used in renewing of theelectrolytic cell, the area of the surface opposed to the membrane inthe electrode for electrolysis is more preferably 0.1 m² or more,further preferably 1 m² or more. The area can be measured by, forexample, a method described in Examples.

The electrode for electrolysis in the present embodiment has a forceapplied per unit mass·unit area of preferably 1.6 N/(mg·cm²) or less,more preferably less than 1.6 N/(mg·cm²), further preferably less than1.5 N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less from the viewpoint of enabling a goodhandling property to be provided and having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, afeed conductor (a degraded electrode and an electrode having no catalystcoating), and the like. The force applied is even still more preferably1.1 N/mg·cm² or less, further still more preferably 1.10 N/mg·cm² orless, particularly preferably 1.0 N/mg·cm² or less, especiallypreferably 1.00 N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0.2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit is preferably 48 mg/cm² or less, more preferably 30mg/cm² or less, further preferably 20 mg/cm² or less from the viewpointof enabling a good handling property to be provided, having a goodadhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and of economy, and furthermore is 15 mg/cm² or lessfrom the comprehensive viewpoint including handling property, adhesion,and economy. The lower limit value is not particularly limited but is ofthe order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by the following method (i) or (ii).The value obtained by the measurement of the method (i) (also referredto as “the force applied (1)”) and the value obtained by the measurementof the method (ii) (also referred to as “the force applied (2)”) may bethe same or different, and either of the values is preferably less than1.5 N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square), and a sample ofelectrode (130 mm square) are laminated in this order. After thislaminate is sufficiently immersed in pure water, excess water depositedon the surface of the laminate is removed to obtain a sample formeasurement. The arithmetic average surface roughness (Ra) of the nickelplate after the blast treatment is 0.5 to 0.8 μm. The specific methodfor calculating the arithmetic average surface roughness (Ra) is asdescribed in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method (i)is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg=i²), even further.preferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. The force ispreferably more than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and furthermore, isfurther more preferably 0.14 N/(mg·cm²), still more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m).

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurement. Under conditionsof a temperature of 23±2° C. and a relative humidity of 30±5%, only thesample of electrode in this sample for measurement is raised in avertical direction at 10 mm/minute using a tensile and compressiontesting machine, and the load when the sample of electrode is raised by10 mm in a vertical direction is measured. This measurement is repeatedthree times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²) even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. Further, the forceis preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/(mg·cm²) or more from theviewpoint of further improving the electrolytic performance, and isfurther more preferably 0.14 N/(mg·cm²) or more from the viewpoint offurther facilitating handling in a large size (e.g., a size of 1.5 m×2.5m).

The electrode for electrolysis in the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 120 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having, no catalyst coating, being capable or being suitably rolled in aroll and satisfactorily folded, and facilitating handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 μm, more preferably 15 μm.

The proportion measured by the following method (2) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint or further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The electrode for electrolysis in the present embodiment preferably hasa porous structure and an opening ratio or void ratio of 5 to 90% orless from the viewpoint of enabling a good handling property to beprovided, having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode (feedconductor), and an electrode (feed conductor) having, no catalystcoating, and preventing accumulation of gas to be generated duringelectrolysis, although not particularly limited. The opening ratio ismore preferably 10 to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V was calculatedfrom the values of the gauge thickness, width, and length of theelectrode, and further, a weight W was measured to thereby calculate anopening ratio A by the following formula.

A=(1−(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio is appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber and,mesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing, themold for forming, voids in the case of foamed metal, or the like.

Hereinbelow, one aspect of the electrode for electrolysis in the presentembodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 43, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also as shown FIG. 43, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 43, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol or the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au,Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, andLu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The curabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Cu, Zn,Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Tr, Pt, Au, Hg,Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, and Lu, andoxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thicknesspreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis is measured in the same manner as thethickness of the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

In the present embodiment, the electrode for electrolysis preferablycontains at least one catalytic component selected from the groupconsisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Y, Zr, Nb, Mo, Ag, Ta, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si,P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy from the viewpoint ofachieving sufficient electrolytic performance.

In the present embodiment, from the viewpoint that the electrode forelectrolysis, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a macroporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, furthermore preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness or 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking or a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst layer is formedon the substrate for electrode for electrolysis by an application stepof applying a coating liquid containing a catalyst, a drying step ofdrying the coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysis isperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable 5 to 20minutes more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 obtained by applying a solution in which metal saltsof various combination are dissolved (first coating liquid) onto thesubstrate for electrode for electrolysis and then pyrolyzing (baking)the coating liquid in the presence of oxygen. The content of the metalin the first coating liquid is substantially equivalent to that in thefirst layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and the further post-bakedfor a long period as required can further improve the stability of thefirst layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating. An exampleincludes a method in which the substrate is fixed in a chamber and themetal ruthenium target is irradiated with an electron beam. Evaporatedmetal ruthenium particles are positively charged in plasma in thechamber to deposit on the substrate negatively charged. The plasmaatmosphere is argon and oxygen, and ruthenium deposits as rutheniumoxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

The electrode for electrolysis in the present embodiment can beintegrated with a membrane such as an ion exchange membrane and amicroporous membrane and used. Thus, the laminate of the presentembodiment can be used as a membrane-integrated electrode. Then, thesubstituting work for the cathode and anode on renewing the electrode iseliminated, and the work efficiency is markedly improved.

The electrode integrated with the membrane such as an ion exchangemembrane and a microporous membrane can make the electrolyticperformance comparable to or higher than those of a new electrode.

Hereinafter, the ion exchange membrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane is not particularly limited as long as themembrane can be laminated with the electrode for electrolysis, andvarious ion exchange membranes may be employed. In the presentembodiment, an ion exchange membrane that has a membrane body containinga hydrocarbon polymer or fluorine-containing polymer having an ionexchange group and a coating layer provided on at least one surface ofthe membrane body is preferably used. It is preferable that the coatinglayer contain inorganic material particles and a binder and the specificsurface area of the coating layer be 0.1 to 10 m²/g. The ion exchangemembrane having such a structure has a small influence of gas generatedduring electrolysis on electrolytic performance and tends to exertstable electrolytic performance.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO₃ ⁻, hereinbelow also referred to as a “sulfonicacid group”) or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂ ⁻,hereinbelow also referred to as a “carboxylic acid group”). From theviewpoint of strength and dimension stability, reinforcement corematerials are preferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 44 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane.

An ion exchange membrane 1 has a membrane body 10 containing ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group and coating layers 11 a and 11 b formed on both thesurfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by —SO₃ ⁻, hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group (a group represented by—CO₂ ⁻, hereinbelow also referred to as a “carboxylic acid group”), andthe reinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane 1, as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, is suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample FIG. 44.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)_(s)—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time or hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having, a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0.5 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane 1, a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer 2 located on the cathode sideof the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane preferably has a coating layer on at least onesurface of the membrane body. As shown in FIG. 44, in the ion exchangemembrane 1, coating layers 11 a and 11 b are formed on both the surfacesof the membrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides or Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durability, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurities suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint or durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contract the ion exchange membrane can be controlled inthe desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as enforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, alkalis, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) is preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area or surface through which substances such as ions(an electrolyte solution and cations contained therein (e.g., sodiumions)) can pass (B) to the area of either one surface of the membranebody (A) (B/A). The total area of the surface through which substancessuch as ions can pass (B) can refer to the total areas of regions inwhich in the ion exchange membrane, cations, an electrolytic solution,and the like are not blocked by the reinforcement core materials and thelike contained in the ion exchange membrane.

FIG. 45 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 45, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting, illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapeof sacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step (4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include amethod in which a fluorine-containing polymer having a carboxylic acidgroup precursor (e.g., carboxylate functional group) (hereinafter, alayer comprising the same is referred to as the first layer) located onthe cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface f the membranebody, the method has a property sufficiently retaining the mechanicalstrength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that is, projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 46(a) and (b) are schematic viewsfor explaining a method for forming the continuous holes of the ionexchange membrane.

FIGS. 46(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 46(a) exemplifies the plain-woven reinforcing material in which thereinforcement yarns 52 and sacrifice yarns 504 a are interwoven alongboth the longitudinal direction and the lateral direction in the paper,and the arrangement of the reinforcement yarns 52 and the sacrificeyarns 504 a in the reinforcing material may be varied as required.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counterion of the ion exchange group by (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example, and ispreferably 80 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

In the present embodiment, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having an EW(ion exchange capacity) different from that of the first ion exchangeresin layer. Additionally, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having afunctional group different from that of the first ion exchange resinlayer. The ion exchange capacity can be adjusted by the functional groupto be introduced, and functional groups that may be introduced are asmentioned above.

[Fixed Region]

In the present embodiment, the electrode for electrolysis is fixed in atleast one region of a surface of the membrane, and in the section of<Third embodiment>, the one or two or more regions are also referred toas fixed regions. The fixed region in the present embodiment is notparticularly limited as long as the region is a portion that has afunction of preventing separation of the electrode for electrolysis fromthe membrane and fixes the membrane onto the electrode for electrolysis.For example, the electrode for electrolysis per se may serve as a fixingmeans to constitute the fixed region, or a fixing member, which isseparate from the electrode for electrolysis, may serve as a fixingmeans to constitute the fixed region. The fixed region in the presentembodiment may be present only at the position corresponding to theconducting surface during electrolysis or may extend to the positioncorresponding to the non-conducting surface. The “conducting surface”corresponds to a portion designed so as to allow electrolytes to migratebetween the anode chamber and the cathode chamber. The “non-conductingsurface” means a portion other than the conducting surface.

Further, in the present embodiment, the proportion of the fixed regionon the surface of the membrane (hereinbelow, simply also referred to as“proportion α”) will be more than 0% and less than 93%. The aboveproportion can be determined as the proportion of the area of the fixedregion (hereinbelow, simply also referred to as the “area S3”) to thearea of the surface of the membrane (hereinbelow, simply also referredto as the “area S1”). In the present embodiment, “the surface of themembrane means the surface of the side on which the electrode forelectrolysis is present among the surfaces possessed by the membrane.The area not covered with the electrode for electrolysis in the surfaceof the membrane mentioned above is also included in the area S1.

From the viewpoint of improving the stability as a laminate of themembrane and the electrode for electrolysis, the proportion α(=100×S3/S1) is preferably 0.00000001% or more, more preferably0.0000001% or more. In contrast, as in the conventional art, in the caseof the membrane and the electrode firmly adhere to each other on theentire contact surface therebetween by a method such as thermalcompression (i.e., the case where the proportion is 100%), the entirecontact surface of the electrode sinks into the membrane to therebyphysically adhere thereto. Such an adhesion portion inhibits sodium ionsfrom migrating in the membrane to thereby markedly raise the voltage. Inthe present embodiment, from the viewpoint of providing a sufficientspace for ions to freely migrate, the above proportion is less than 93%,preferably 90% or less, more preferably 70% or less, further preferablyless than 60%.

In the present embodiment, from the viewpoint of achieving betterelectrolytic performance, it is preferable to adjust the area of theportion corresponding only to the conducting surface (hereinbelow,simply also referred to as the “area S3′”) of the area of the fixedregion (area S3). That is, it is preferable to adjust the proportion ofthe area S3′ (hereinbelow, simply also referred to as the “proportionβ”) to the area of the conducting surface (hereinbelow, simply alsoreferred to as the “area S2”). The area S2 can be identified as thesurface area of the electrode for electrolysis (the details will bementioned below). Specifically, in the present embodiment, theproportion β (=100×S3′/S2) is preferably more than 0% and less than100%, more preferably 0.0000001% or more and less than 83%, furtherpreferably 0.000001% or more and 70% or less, even further preferably0.00001% or more and 25% or less.

The proportions α and β described above can be measured, for example, asfollows.

First, the area of the surface of the membrane S1 is calculated. Then,the area of the electrode for electrolysis S2 is calculated. The areasS1 and S2 herein can be identified as the area when the laminate of themembrane and the electrode for electrolysis is viewed from the side ofthe electrode for electrolysis (see FIG. 57).

The form of the electrode for electrolysis is not particularly limited,and the electrode may have openings. In the case where the form is netor the like, which has openings, and the opening ratio is less than 90%(i), as for S2, the opening portions thereof are included in the areaS2. In contrast, in the case where the opening ratio is 90% or more(ii), the area excluding the opening portions is used to calculate S2 inorder to achieve electrolytic performance sufficiently. The openingratio referred to herein is a numerical value (%; 100×S′/S″) obtained bydividing the total area of the opening portions S′ in the electrode forelectrolysis by the area in the electrode for electrolysis S″, which isobtained when the opening portions are included in the area.

The area of the fixed region (area S3 and area S3′) will be mentionedbelow.

As described above, the proportion of the region α(%) on the surface ofthe membrane can be determined by calculating 100×(S3/S1). Additionally,the proportion of the area of the portion only corresponding to theconducting surface of the fixed region β (%) relative to the area of theconducting surface can be determined by calculating 100×(S3′/S2).

More specifically, measurement can be performed by a method described inExample mentioned below.

The area of the surface of the membrane S1 to be identified as mentionedabove is not particularly limited, but is preferably 1 time or more and5 times or less, more preferably 1 time or more and 4 times or less,further preferably 1 time or more and 3 times or less the area of theconducting surface S2.

In the present embodiment, a fixing configuration in the fixed region isnot intended to be limited, but, for example, a fixing configurationexemplified below can be employed. Only one fixing configuration can beemployed, or two or more fixing configurations can be employed incombination.

In the present embodiment, at least a portion of the electrode forelectrolysis preferably penetrates the membrane and thereby is fixed inthe fixed region. The aspect will be described by use of FIG. 47A.

In FIG. 47A, at least a portion of the electrode for electrolysis 2penetrates the membrane 3 and thereby is fixed. As shown in FIG. 47A,the portion of the electrode for electrolysis 2 is penetrating themembrane 3. FIG. 47A shows an example in which the electrode forelectrolysis 2 is a metal porous electrode. That is, in FIG. 47A, aplurality of portions of the electrode for electrolysis 2 are separatelyshown, but these portions are continuous. Thus, the cross-section of anintegral metal porous electrode shown (the same applies to FIGS. 48 to51 below).

In the electrode configuration, when the membrane 3 in the predeterminedposition (position to be the fixed region), for example, is pressed ontothe electrode for electrolysis 2, a portion of the membrane 3 intrudesinto the asperity geometry or opening geometry on the surface of theelectrode for electrolysis 2. Then, recesses on the electrode surfaceand projections around openings penetrate the membrane 3 and preferablypenetrate through to the outer surface 3 b of the membrane 3, as shownin FIG. 47A.

As described above, the fixing configuration in FIG. 47A can be producedby pressing the membrane 3 onto the electrode for electrolysis. In thiscase, the membrane 3 is softened by warming and then subjected tothermal compression and thermal suction. Then, the electrode forelectrolysis 2 penetrates the membrane 3. Alternatively, the membrane 3may be used in a melt state. In this case, the membrane 3 is preferablysuctioned from the side of the outer surface 2 b (back surface side) ofthe electrode for electrolysis 2 in the state shown in FIG. 47B. Theregion in which the membrane 3 is pressed onto the electrode forelectrolysis 2 constitutes the “fixed region”.

The fixing configuration shown in FIG. 47A can be observed by amagnifier (loupe), optical microscope, or electron microscope. Since theelectrode for electrolysis 2 has penetrated the membrane 3, it ispossible to estimate the fixing configuration in FIG. 47A by a test ofthe conduction between the outer surface 3 b of the membrane 3 and theouter surface 2 b of the electrode for electrolysis 2 by use of a testeror the like.

In FIG. 47A, no electrolyte solution in the anode chamber and thecathode chamber partitioned by the membrane preferably permeates thepenetration portion. Thus, the pore size at the penetration portion ispreferably small enough not to allow the electrolyte solution topermeate the portion. Specifically, characteristics comparable to thoseof a membrane having no penetration portion are preferably exerted whenan electrolytic test is performed. Alternatively, the penetrationportion is preferably subjected to processing for preventing permeationof the electrolyte solution. It is preferable to use, in the penetrationportion, a material that is not eluted or decomposed by the anodechamber electrolyte solution, products to be generated in the anodechamber, the cathode chamber electrolyte solution, and products to begenerated in the cathode chamber. For example, EPDM andfluorine-containing resins are preferable. A fluorine resin having anion exchange group is more preferable.

In the present embodiment, at least a portion of the electrode forelectrolysis is preferably located inside the membrane and thereby fixedin the fixed region. The aspect will be described by use of FIG. 48A.

As described above, the surface of the electrode for electrolysis 2 hasan asperity geometry or opening geometry. In the embodiment shown inFIG. 48A, a portion of the electrode surface enters the membrane 3 inthe predetermined position (position to be the fixed region) and isfixed thereto. The fixing configuration shown in FIG. 48A can beproduced by pressing the membrane 3 onto the electrode for electrolysis2. In this case, the fixing configuration in FIG. 48A is preferablyformed by softening the membrane 3 by warming and then thermallycompressing and thermally suctioning the membrane 3. Alternatively, thefixing configuration in FIG. 48A can be formed by melting the membrane3. In this case, the membrane 3 preferably suctioned from the side ofthe outer surface 2 b (back surface side) of the electrode forelectrolysis 2.

The fixing configuration shown in FIG. 48A can be observed by amagnifier (loupe), optical microscope, or electron microscope.Particularly preferable is a method including subjecting the sample toan embedding treatment, then forming a cross-section by a microtome, andobserving the cross-section. In the fixing configuration shown in FIG.48A, the electrode for electrolysis does not penetrate the membrane 3.Thus, no conduction between the outer surface 3 b of the membrane 3 andthe outer surface 2 b of the electrode for electrolysis 2 is identifiedby the conduction test.

In the present embodiment, it is preferable to additionally have afixing member for fixing the membrane and the electrode forelectrolysis. The aspect will be described by use of FIGS. 49A to C.

The fixing configuration shown in FIG. 49A is a configuration in which afixing member 7, which is separate from the electrode for electrolysis 2and the membrane 3, is used and the fixing member 7 penetrates andthereby fixes the electrode for electrolysis 2 and the membrane 3. Theelectrode for electrolysis 2 is not necessarily penetrated by the fixingmember 7, and should be fixed by the fixing member 7 so as not to beseparated from the membrane 2. The material for the fixing member 7 isnot particularly limited, and materials constituted by metal, resin, thelike, for example, can be used as the fixing member 7. Examples of themetal include nickel, nichrome, titanium, and stainless steel (SUS).Oxides thereof may be used. Examples of the resin that can be usedinclude fluorine resins (e.g., polytetrafluoroethylene (PTFE),copolymers of tetrafluoroethylene and perfluoroalkoxy ethylene (PFA),copolymers of tetrafluoroethylene and ethylene (ETFE), materials for themembrane 3 described below, polyvinylidene fluoride (PVDF),ethylene-propylene-diene rubber (EPDM), polyethylene (PP), polypropylene(PE), on, and aramid.

In the present embodiment, for example, a yarn-like fixing member(yarn-like metal or resin) is used to sew the predetermined position(position to be the fixed region) between the outer surface 2 b of theelectrode for electrolysis 2 and the outer surface 3 b of the membraneas shown in FIGS. 49B and C. The yarn-like resin is not particularlylimited, but examples thereof include PTFE yarns. It is also possible tothe electrode for electrolysis 2 to the membrane 3 by use of a fixingmechanism such as a tucker.

In FIGS. 49A to C, no electro solution in the anode chamber and thecathode chamber partitioned by membrane preferably permeates thepenetration portion. Thus, the pore size at the penetration portion ispreferably small enough not to allow the electrolyte solution topermeate the portion. Specifically, characteristics comparable to thoseof a membrane having no penetration portion are preferably exerted whenan electrolytic test is performed. Alternatively, the penetrationportion is preferably subjected to processing for preventing permeationof the electrolyte solution. It is preferable to use, in the penetrationportion, a material that is not eluted or decomposed by the anodechamber electrolyte solution, products to be generated in the anodechamber, the cathode chamber electrolyte solution, and products to begenerated in the cathode chamber. For example, EPDM andfluorine-containing resins are preferable. A fluorine resin having anion exchange group is more preferable.

The fixing configuration shown in FIG. 50 is a configuration in whichfixing is made by an organic resin (adhesion layer) interposed betweenthe electrode for electrolysis 2 and the membrane 3. That is, in FIG.50, shown is a configuration in which an organic resin as the fixingmember 7 is arranged on the predetermined position (position to be thefixed region) between the electrode for electrolysis 2 and the membrane3 to thereby make fixing by adhesion. For example, the organic resin isapplied onto the inner surface 2 a of the electrode for electrolysis 2,the inner surface 3 a of the membrane 3, or one or both of the innersurface 2 a of the electrode for electrolysis 2 and the inner surface 3a of the membrane 3. Then, the fixing configuration shown in FIG. 50 canbe formed by laminating the electrode for electrolysis 2 to the membrane3. The materials for the organic resin are not particularly limited, butexamples thereof that can be used include fluorine resins (e.g., PTFE,PFA, and ETFE) and resins similar to the materials constituting themembrane 3 as mentioned above. Commercially availablefluorine-containing adhesives and PTFE dispersions also can be used asappropriate. Additionally, multi-purpose vinyl acetate adhesives,ethylene-vinyl acetate copolymer adhesives, acrylic resin adhesives,α-olefin adhesives, styrene-butadiene rubber latex adhesives, vinylchloride resin adhesives, chloroprene adhesives, nitrile rubberadhesives, urethane rubber adhesives, epoxy adhesives, silicone resinadhesives, modified silicone adhesives, epoxy-modified silicone resinadhesives, silylated urethane resin adhesives, cyanoacrylate adhesives,and the like also can be used.

In the present embodiment, organic resins that dissolve in anelectrolyte solution or dissolve or decompose during electrolysis may beused. Examples of the organic resins that dissolve in an electrolytesolution or dissolve or decompose during electrolysis include, but arenot limited to, vinyl acetate adhesives, ethylene-vinyl acetatecopolymer adhesives, acrylic resin adhesives, α-olefin adhesives,styrene-butadiene rubber latex adhesives, vinyl chloride resinadhesives, chloroprene adhesives, nitrile rubber adhesives, urethanerubber adhesives, epoxy adhesives, silicone resin adhesives, modifiedsilicone adhesives, epoxy-modified silicone resin adhesives, silylatedurethane resin adhesives, and cyanoacrylate adhesives.

The fixing configuration shown in FIG. 50 can be observed by an opticalmicroscope or electron microscope. Particularly preferable is a methodincluding subjecting the sample to an embedding treatment, then forminga cross-section by a microtome, and observing the cross-section.

In the present embodiment, at least a portion of the fixing memberpreferably externally grips the membrane and the electrode forelectrolysis. The aspect will be described by use of FIG. 51A.

The fixing configuration shown in FIG. 51A is a configuration in whichthe electrode for electrolysis 2 and membrane 3 are externally grippedand fixed. That is, the outer surface 2 b of the electrode forelectrolysis 2 and the outer surface 3 b of the membrane 3 aresandwiched and fixed by a gripping member as the fixing member 7 in thefixing configuration shown in FIG. 51A, a state in which the grippingmember is engaging in the electrode for electrolysis 2 and the membrane3 is also included. Examples of the gripping member include tape andclips.

In the present embodiment, a gripping member that dissolves in anelectrolyte solution may be used. Examples of the gripping member thatdissolves in an electrolyte solution include PET tape and clips and PVAtape and clips.

In the fixing configuration shown in FIG. 51A, unlike those in FIGS. 47to FIG. 50, the electrode for electrolysis 2 and the membrane 3 are notbonded at the interface therebetween, but the inner surface 2 a of theelectrode for electrolysis 2 and the inner surface 3 a of the membrane 3are only abutted or opposed to each other. Removal of the grippingmember can release the fixed state of the electrode for electrolysis 2and the membrane 3 and separate the electrode for electrolysis 2 fromthe membrane 3.

Although not shown in FIG. 51A, it is also possible to fix the electrodefor electrolysis 2 and the membrane 3 using a gripping member in anelectrolytic cell.

For example, it is possible to fold PTFE tape back to fix the membraneand the electrode in a sandwich manner.

Also in the present embodiment, at least a portion of the fixing memberpreferably fixes the membrane and the electrode for electrolysis bymagnetic force. The aspect will be described by use of FIG. 51B.

The fixing configuration shown in FIG. 51B is a configuration in whichthe electrode for electrolysis 2 and membrane 3 are externally grippedand fixed. The difference from that in FIG. 51A is that a pair ofmagnets are used as the gripping member, which is the fixing member. Inthe aspect of the fixing configuration shown in FIG. 51B, a laminate 1is attached to the electrolyzer. Thereafter, during operation of theelectrolyzer, the gripping member may be left as it or may be removedfrom the laminate 1.

Although not shown FIG. 51d , it is also possible to fix the electrodefor electrolysis 2 and the membrane 3 using a gripping member in anelectrolytic cell. When a magnetic material that adheres to magnets isused as a part of the material for the electrolytic cell, one grippingmaterial placed on the side of the membrane surface. Then, the grippingmaterial and the electrolytic cell car sandwich and fix the electrodefor electrolysis 2 and the membrane 3 therebetween.

A plurality of fired region lines can be provided. That is, 1, 2, 3, . .. n fixed region lines can be arranged from the side f the contourtoward the inner side of the laminate 1. n is an integer of 1 or more.The m-th (m<n) fixed region line an the L-th (m<L≤n) fixed region linecan be each formed to have a different fixation pattern.

A fixed region line to be formed in the electroconductive portionpreferably has a line-symmetric shape. This tends to enable stressconcentration to be controlled. For example, when two orthogonallyintersecting directions are referred to as the X direction and the Ydirection, it is possible to configure the fixed region by arranging afixed region line each in the X direction and the Y direction orarranging a plurality of fixed region lines at equal intervals each inthe X direction and the Y direction. The number of fixed region lineseach in the X direction and the Y direction is not limited, but ispreferably 100 or less each in the X direction and the Y direction. Fromthe viewpoint of achieving the planarity of electroconductive portion,the number of fixed region lines is preferably 50 or less each in the Xdirection and the Y direction.

When the fixed region in the present embodiment has the fixingconfiguration shown in FIG. 47A or FIG. 49, a sealing material ispreferably applied onto the membrane surface of the fixed region fromthe viewpoint of preventing a short circuit caused by a contact betweenthe anode and the cathode. As the sealing material, the materialsdescribed for the above adhesives can be used.

When a fixing member is used, on determining the area S3 and the areaS3′, as for the portion at which the fixing member overlaps, theoverlapping part is not included in the area S3 and the area S3′. Forexample, when fixing is made by using the PTFE yarns mentioned above asthe fixing members, the portion at which the PTFE yarns intersect witheach other is not included as an overlapping part in the area. Whenfixing is made by using the PTFE tapes mentioned above as the fixingmembers, the portion at which the PTFE tapes intersect with each otheris not included as an overlapping part in the area.

When fixing is made by using the PTFE yarn or adhesive mentioned aboveas the fixing member, the area present on the back side of the electrodefor electrolysis and/or membrane is also included in the area S3 andarea S3′.

The laminate in the present embodiment may have various fixed regions invarious positions as mentioned above, but the electrode for electrolysispreferably satisfies the “force applied” mentioned above particularly ina portion in which no fixed region is present (non-fixed region). Thatis, the force applied per unit-mass unit area of the electrode forelectrolysis in the non-fixed region is preferably less than 1.5N/mg·cm².

[Electrolyzes]

The electrolyzer of the present embodiment includes the laminate of thepresent embodiment. Hereinafter, the case of performing common saltelectrolysis by using an ion exchange membrane as the membrane is takenas an example, and one embodiment of the electrolyzer will be describedin detail.

[Electrolytic Cell]

FIG. 52 illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell 1 has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 56, and the cathode 21 and the reverse currentabsorbing layer 18 b are electrically connected. The cathode chamber 20further has a collector 23, a support 24 supporting the collector, and ametal elastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer may be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support 24, the support 24 and the collector 23, and the collector23 and the metal elastic body 22 are each directly attached and thecathode 21 is laminated on the metal elastic body 22. Examples of amethod for directly attaching these constituent members to one anotherinclude welding and the like. Alternatively, the reverse currentabsorber 18, the cathode 21, and the collector 23 may be collectivelyreferred to as a cathode structure 40.

FIG. 53 illustrates a cross-sectional view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 54 shows an electrolyzer4. FIG. 55 shows a step of assembling the electrolyzer 4. As shown inFIG. 53, an electrolytic cell 1, a cation exchange membrane 2, and anelectrolytic cell 1 are arranged in series in the order mentioned. Anion exchange membrane 2 is arranged between the anode chamber of oneelectrolytic cell 1 among the two electrolytic cells that are adjacentin the electrolyzer and the cathode chamber of the other electrolyticcell 1. That is, the anode chamber 10 of the electrolytic cell 1 and thecathode chamber 20 of the electrolytic cell 1 adjacent thereto isseparated by the cation exchange membrane 2. As shown in FIG. 54, theelectrolyzer 4 is composed of a plurality of electrolytic cells 1connected in series via the ion exchange membrane 2. That is, theelectrolyzer 4 is a bipolar electrolyzer comprising the plurality ofelectrolytic cells 1 arranged in series and ion exchange membranes 2each arranged between adjacent electrolytic cells 1. As shown in FIG.55, the electrolyzer 4 is assembled by arranging the plurality ofelectrolytic cells 1 in series via the ion exchange membrane 2 andcoupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine is electrolyzed, chlorine gas is generated onthe side of the anode 11, and sodium hydroxide (solute) and hydrogen gasare generated on the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Whenthe electrode for electrolysis in the present embodiment is inserted tothe anode side, 11 serves as the anode feed conductor. When theelectrode for electrolysis in the present embodiment is not inserted tothe anode side, 11 serves as the anode. The anode chamber 10 has ananode side electrolyte solution supply unit that supplies an electrolytesolution to the anode chamber 10, a baffle plate that is arranged abovethe anode-side electrolyte solution supply unit so as to besubstantially parallel or oblique to the partition wall 30, and ananode-side gas liquid separation unit arranged above the baffle plate toseparate gas from the electrolyte solution including the gas mixed.

(Anode)

When the electrode for electrolysis in the present embodiment is notinserted to the anode side, the anode 11 is provided in the frame of theanode chamber 10. As the anode 11, a metal electrode such as so-calledDSA(R) can be used. DSA is an electrode including a titanium substrateof which surface is covered with an oxide comprising ruthenium, iridium,and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame or the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatvely, DSA having athinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode and parallel to the bottom 19 of theelectrolytic cell is preferable because the electrolyte solution can beuniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 52,and below means the lower direction in the electrolytic cell 1 in FIG.52.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 in the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 52, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis in thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis in thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis in the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20. The cathode 21 preferably has a nickel substrateand a catalyst layer that covers the nickel substrate. Examples of thecomponents of the catalyst layer on the nickel substrate include metalssuch as Ru, C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr,Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Ph, Bi,La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, andoxides and hydroxides of the metals. Examples of the method for formingthe catalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. The cathode 21 may be subjected to areduction treatment, as required. As the substrate of the cathode 21,nickel, nickel alloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. Nickel, nickel alloys, andnickel-plated iron or stainless, having no catalyst coating may be used.As the substrate of the cathode feed conductor 21, nickel, nickelalloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, and titanium. The collector 23 may be amixture, alloy, or composite oxide of these metals. The collector 23 mayhave any form as long as the form enables the function of the collectorand may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electrolytic cells 1 connected in series. Lowering of thevoltage enables the power consumption to be reduced. With the metalelastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis according to the present embodiment is placed in theelectrolytic cell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality supports 24 are arranged between the partitionwall 30 and the collector 23. The plurality of supports 24 are alignedsuch that the surfaces thereof are in parallel to each other. Thesupports 24 are arranged substantially perpendicular to the partitionwall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane (see FIGS. 52 and 53). These gaskets can impart airtightness toconnecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced gas and be usable for a long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 53), each electrolytic cell 1 onto which the gasketis attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

(Ion Exchange Membrane 2)

The ion exchange membrane 2 is as described in the section of the ionexchange membrane described above.

(Water Electrolysis)

The electrolyzer of the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

Fourth Embodiment

Here, a fourth embodiment of the present invention will be described indetail with reference to FIGS. 63 to 90.

[Electrolyzer]

The electrolyzer according to the fourth embodiment (hereinafter, in thesection of <Fourth embodiment>, simply referred to as “the presentembodiment”) comprises an anode, an anode frame that supports the anode,an anode side gasket that is arranged on the anode frame, a cathode thatis opposed to the anode, a cathode frame that supports the cathode, acathode side gasket that is arranged on the cathode frame and is opposedto the anode side gasket, and a laminate of a membrane and an electrodefor electrolysis, the laminate being arranged between the anode sidegasket and the cathode side gasket, wherein at least a portion of thelaminate is sandwiched between the anode side gasket and the cathodeside gasket, and a ventilation resistance is 24 kPa·s/m or less when theelectrode for electrolysis has a size of 50 mm×50 mm, the ventilationresistance being measured under conditions of a temperature of 24° C., arelative humidity of 32%, a piston speed of 0.2 cm/s, and a ventilationvolume of 0.4 cc/cm²/s. As configured described above, the electrolyzerof the present embodiment has excellent electrolytic performance as wellas can prevent damage of the membrane.

The electrolyzer of the present embodiment comprises the constituentmembers mentioned above, in other words, comprises an electrolytic cell.Hereinafter, a case of performing common salt electrolysis by using anion exchange membrane as the membrane is taken as an example, and oneembodiment of the electrolyzer will be described in detail.

[Electrolytic Cell]

First, the electrolytic cell, which can be used as a constituent unit ofthe electrolyzer of the present embodiment, will be described. FIG. 63illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell 1 has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 67, and the cathode 1 and the reverse current absorbinglayer 18 b are electrically connected. The cathode chamber 20 furtherhas a collector 23, a support 24 supporting the collector, and a metalelastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer may be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support 24, the support 24 and the collector 23, and the collector23 and the metal elastic body 22 are each directly attached and thecathode 21 is laminated on the metal elastic body 22. Examples of amethod for directly attaching these constituent members to one anotherinclude welding and the like. Alternatively, the reverse currentabsorber 18, the cathode 21, and the collector 23 may be collectivelyreferred to as a cathode structure 40.

FIG. 64 illustrates a cross-sectional view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 65 shows an electrolyzer4. FIG. 66 shows a step of assembling the electrolyzer 4.

In a conventional electrolyzer, as shown in FIG. 64A, an electrolyticcell 1, a membrane (herein, a cation exchange membrane) 2, and anelectrolytic cell 1 are arranged in series in the order mentioned. Theion exchange membrane 2 is arranged between the anode chamber of oneelectrolytic cell 1 of the two electrolytic cells that are adjacent inthe electrolyzer and the cathode chamber of the other electrolytic cell1. That is, in the electrolyzer, the anode chamber 10 of theelectrolytic cell 1 and the cathode chamber 20 of the electrolytic cell1 adjacent thereto are usually separated by the cation exchange membrane2.

Meanwhile, the present embodiment, as shown in FIG. 64B, an electrolyticcell 1, a laminate 25 having a membrane (herein, a cation exchangemembrane) 2, and an electrode for electrolysis (herein, a cathode forrenewal) 21 a, and an electrolytic cell 1 are arranged in series in theorder mentioned. The laminate 25, at the portion thereof (in FIG. 64B,the top end portion), is sandwiched between an anode gasket 12 and acathode gasket 13.

As shown in FIG. 65, the electrolyzer 4 is composed of a plurality ofelectrolytic cells 1 connected in series via the ion exchange membrane2. That is, the electrolyzer 4 is a bipolar electrolyzer comprising theplurality of electrolytic cells 1 arranged in series and ion exchangemembranes 2 each arranged between adjacent electrolytic cells 1. Asshown in FIG. 66, the electrolyzer 4 is assembled by arranging theplurality of electrolytic cells 1 connected in series via the ionexchange membrane 2 and coupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That is, the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine is electrolyzed, chlorine gas is generated onthe side of the anode 11, and sodium hydroxide (solute) and hydrogen gasare generated on the side of the cathode 21.

As mentioned above, the characteristics of the membrane, cathode, andanode in the electrolyzer deteriorate usually in association withoperation of the electrolyzer and replacement by new ones becomerequired before long. In the case of replacement of only the membrane,renewing can be easily performed by extracting the existing membranebetween the electrolytic cells and inserting a new membranetherebetween, but replacement of the anode or the cathode by means ofwelding is complicated because a specialized installation is required.

Meanwhile, in the present embodiment, the laminate 25, at the portionthereof (in FIG. 64B, the top end portion), is sandwiched between ananode gasket 12 and a cathode gasket 13, as described above.Particularly in the example shown in FIG. 64B, the membrane (herein, thecation exchange membrane) 2 and the electrode for electrolysis (herein,the cathode for renewal) 21 a can be fixed in at least the top endportion of the laminate by pressing in the direction from the anodegasket 12 toward the laminate 25 and pressing in the direction from thecathode gasket 13 toward the laminate 25. This case is preferablebecause it is not necessary to fix the laminate 25 (in particular, theelectrode for electrolysis) on the existing member (e.g., the existingcathode) by welding. That is, the case where both the electrode forelectrolysis and the membrane are sandwiched between the anode sidegasket and the cathode side gasket is preferable because the workefficiency during electrode renewing in the electrolyzer tends to beimproved.

Further, in accordance with the configuration of the electrolyzer of thepresent embodiment, the membrane and the electrode for electrolysis aresufficiently fixed as the laminate, and thus, excellent electrolyticperformance can be achieved.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Thefeed conductor herein referred to means a degraded electrode (i.e., theexisting electrode), an electrode having no catalyst coating, and thelike. When the electrode for electrolysis in the present embodiment isinserted to the anode side, 11 serves as an anode feed conductor. Whenthe electrode for electrolysis the present embodiment is not inserted tothe anode side, 11 serves as an anode. The anode chamber 10 preferablyhas an anode-side electrolyte solution supply unit that supplies anelectrolyte solution to the anode chamber 10, a baffle plate that isarranged above the anode-side electrolyte solution supply unit so as tobe substantially parallel or oblique to a partition wall 30, and ananode-side gas liquid separation unit that is arranged above the baffleplate to separate gas from the electrolyte solution including the gasmixed.

(Anode)

When the electrode for electrolysis in the present embodiment is notinserted to the anode side, an anode 11 is provided in the frame of theanode chamber 10 (i.e., the anode frame). As the anode 11, a metalelectrode such as so-called DSA(R) can be used. DSA is an electrodeincluding a titanium substrate of which surface is covered with an oxidecomprising ruthenium, iridium, and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA havingthinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is Preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 63,and below means the lower direction in the electrolytic cell 1 in FIG.63.

During electrolysis, produced gas generated in the electrolytic cell andthe electrolyte solution form a mixed phase (gas-liquid mixed phase),which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 in the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electro solution (brine or the like) to circulate internally in theanode chamber 10 to thereby make the concentration uniform. In order tocause internal circulation, the baffle plate is preferably arranged soas to separate the space in proximity to the anode 11 from the space inproximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 63, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis in thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis in thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis in the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20 (i.e., the cathode frame). The cathode 21preferably has a nickel substrate and a catalyst layer that covers thenickel substrate. Examples of the components of the catalyst layer onthe nickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V,Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta,W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb,Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.Examples of the method for forming the catalyst layer include plating,alloy plating, dispersion/composite plating, CVD, PVC, pyrolysis, andspraying. These methods may be used in combination. The catalyst layermay have a plurality of layers and a plurality of elements, as required.The cathode 21 may be subjected to a reduction treatment, as required.As the substrate of the cathode 21, nickel, nickel alloys, andnickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. Nickel, nickel alloys, andnickel-plated iron or stainless, having no catalyst coating may be used.As the substrate of the cathode feed conductor 21, nickel, nickelalloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electrolytic cells 1 connected in series. Lowering of thevoltage enables the power consumption to be reduced. With the metalelastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis in the present embodiment is placed in the electrolyticcell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantially perpendicular to thepartition wall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the laminate 25 (seeFIG. 64B). These gaskets can impart airtightness to connecting pointswhen the plurality of electrolytic cells 1 is connected in series viathe laminate 25.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced gas and be usable for a long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Sandwiching the laminate 25 by theanode gasket and cathode gasket can prevent the electrolyte solution,alkali metal hydroxide, chlorine gas, hydrogen gas, and the likegenerated from electrolysis from leaking out of the electrolytic cells1.

[Laminate]

The laminate in the present embodiment comprises a membrane and anelectrode for electrolysis. The laminate in the present embodiment canimprove the work efficiency during electrode renewing an electrolyzerand further, can exhibit excellent electrolytic performance also afterrenewing. That is, according to the laminate in the present embodiment,on renewing the electrode, the electrode can be renewed by a work assimple as renewing the membrane without a complicated work such asstripping off the existing electrode fixed on the electrolytic cell, andthus, the work efficiency is markedly improved.

Further, according to the laminate in the present embodiment, it ispossible to maintain the electrolytic performance of the existingelectrolytic cell comparable to those of a new electrode or improve theelectrolytic performance. Thus, the electrode fixed on the existingelectrolytic cell and serving as the anode or cathode is only requiredto serve as a feed conductor. Thus, it is also possible to markedlyreduce or eliminate catalyst coating.

[Electrode for Electrolysis]

In the electrode for electrolysis in the present embodiment, theventilation resistance is 24 kPa·s/m or less when the electrode forelectrolysis has a size of 50 mm×50 mm, the ventilation resistance beingmeasured under conditions of the temperature of 24° C., the relativehumidity of 32%, a piston speed of 0.2 cm/s, and a ventilation volume of0.4 cc/cm²/s (hereinbelow, also referred to as “measurement condition1”) (hereinbelow, also referred to as “ventilation resistance 1”). Alarger ventilation resistance means that air is unlikely to flow andrefers to a state of a high density. In this state, the product fromelectrolysis remains in the electrode and a reaction substrate is moreunlikely to diffuse inside the electrode, and thus, the electrolyticperformance (such as voltage) deteriorates. The concentration on themembrane surface increases. Specifically, the caustic concentrationincreases on the cathode surface, and the supply of brine decreases onthe anode surface. As a result, the product accumulates at a highconcentration on the interface at which the membrane is in contact withthe electrode. This accumulation leads to damage of the membrane andalso leads to increase in the voltage and damage of the membrane on thecathode surface and damage of the membrane on the anode surface. In thepresent embodiment, in order to prevent these defects, the ventilationresistance is set at 24 kPa·s/m or less.

In the present embodiment, when the ventilation resistance is largerthan a certain value, NaOH generated in the electrode tends toaccumulate on the interface between the electrode and membrane to resultin a high concentration in the case of the cathode, and the supply ofbrine tends to decrease to cause the brine concentration to be lower inthe case of the anode. In order to prevent damage to the membrane thatmay be caused by such accumulation, the ventilation resistance ispreferably less than 0.19 kPa·s/m, more preferably 0.15 kPa·s/m or less,further preferably 0.07 kPa·s/m or less.

In contrast, when the ventilation resistance is low, the area of theelectrode becomes smaller, and the electroconductive area is reduced.Thus, the electrolytic performance (such as voltage) deteriorates. Whenthe ventilation resistance is zero, the feed conductor functions as theelectrode because no electrode for electrolysis is provided and theelectrolytic performance (such as voltage) markedly deteriorates. Fromthis viewpoint, a preferable lower limit value identified as theventilation resistance 1 is not particularly limited, but is preferablymore than 0 kPa·s/m, more preferably 0.0001 kPa·s/m or more, furtherpreferably 0.001 kPa·s/m or more.

When the ventilation resistance 1 is 0.07 kPa·s/m or less, a sufficientmeasurement accuracy may not be achieved because of the measurementmethod therefor. From this viewpoint, it is also possible to evaluate anelectrode for electrolysis having a ventilation resistance 1 of 0.07kPa·s/m or less by means of a ventilation resistance (hereinbelow, alsoreferred to as “ventilation resistance 2”) obtained by the followingmeasurement method (hereinbelow, also referred to as “measurementcondition 2”). That is, the ventilation resistance 2 is a ventilationresistance measured, when the electrode for electrolysis has a size of50 mm×50 mm, under conditions of the temperature of 24° C., the relativehumidity of 32%, a piston speed of 2 cm/s, and a ventilation volume of 4cc/cm²/s.

The specific methods for measuring the ventilation resistances 1 and 2are described in Examples.

The ventilation resistances 1 and 2 can be within the range describedabove by appropriately adjusting an opening ratio, thickness of theelectrode, and the like, for example. More specifically, for example,when the thickness is constant, a higher opening ratio tends to lead tosmaller ventilation resistances 1 and 2, and a lower opening ratio tendsto lead to larger ventilation resistances 1 and 2.

The electrode for electrolysis in the present embodiment has a forceapplied per unit mass·unit area of preferably 1.6 N/(mg·cm²) or less,more preferably less than 1.6 N/(mg·cm²), further preferably less than1.5 N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less from the viewpoint of enabling a goodhandling property to be provided and having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, afeed conductor (a degraded electrode and an electrode having no catalystcoating), and the like. The force applied is even still more preferably1.1 N/mg·cm² or less, further still more preferably 1.10 N/mg·cm² orless, particularly preferably 1.0 N/mg·cm² or less, especiallypreferably 1.00 N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0.2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit is preferably 48 mg/cm² or less, more preferably 30mg/cm² or less, further preferably 20 mg/cm² or less from the viewpointof enabling a good handling property to be provided, having a goodadhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and of economy, and furthermore is preferably 15mg/cm² or less from the comprehensive viewpoint including handlingproperty, adhesion, and economy. The lower limit value is notparticularly limited but is of the order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as detailed in Examples. As for the force applied, thevalue obtained by the measurement of the method (i) (also referred to as“the force applied (1)”) and the value obtained by the measurement ofthe method (ii) (also referred to as “the force applied (2)”) may be thesame or different, and either of the values is preferably less than 1.5N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode (130 mm square) are laminated in this order.After this laminate is sufficiently immersed in pure water, excess waterdeposited on the surface of the laminate is removed to obtain a samplefor measurement. The arithmetic average surface roughness (Ra) of thenickel plate after the blast treatment is 0.5 to 0.8 μm. The specificmethod for calculating the arithmetic average surface roughness (Ra) isas described in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method ispreferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. The force ispreferably more than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and furthermore, isfurther more preferably 0.14 N/(mg·cm²) still more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m).

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurement. Under conditionsof a temperature of 23±2° C. and a relative humidity of 30±5% only thesample of electrode in this sample for measurement is raised in avertical direction at 10 mm/minute using a tensile and compressiontesting machine, and the load when the sample of electrode is raised by10 mm in a vertical direction is measured. This measurement is repeatedthree times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particular preferably 1.0 N/mg·cm² orless, especially preferably 1.00 N/mg·cm² or less. Further, the force ispreferably more than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and is further morepreferably 0.14 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The electrode for electrolysis in the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 170 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, being capable of being suitably rolled in aroll and satisfactorily folded, and facilitating handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 μm, more preferably 15 μm.

The proportion measured by the following method (2) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint of further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The value obtained by measurement by the following method (A) of theelectrode for electrolysis in the present embodiment is preferably 40 mmor less, more preferably 29 mm or less, further preferably 19 mm or lessfrom the viewpoint of the handling property.

[Method (A)]

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, a sample obtained by laminating an ion exchange membrane which isobtained by applying inorganic material particles and a binder to bothsurfaces of a membrane of a perfluorocarbon polymer into which an ionexchange group is introduced (170 mm square, the details of the ionexchange membrane referred to herein are as described in Examples) andthe electrode for electrolysis is wound around and fixed onto a curvedsurface of a core material being made of polyvinyl chloride and havingan outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter,when the electrode for electrolysis is separated from the sample andplaced on a flat plate, heights in a vertical direction at both edges ofthe electrode for electrolysis L1 and L2 are measured, and an averagevalue thereof is used as a measurement value.

The electrode for electrolysis in the present embodiment preferably hasa porous structure and an opening ratio or void ratio of 5 to 90% orless from the viewpoint of enabling a good handling property to beprovided, having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode (feedconductor), and an electrode (feed conductor) having no catalystcoating, and preventing accumulation of gas to be generated duringelectrolysis, although not particularly limited. The opening ratio ismore preferably 10 to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V was calculatedfrom the values of the gauge thickness, width, and length of theelectrode, and further, a weight W was measured to thereby calculate anopening ratio A by the following formula.

A=(1−(V×ρ))×100

ρ is the density of the electrode material (g/cm³) For example, ρ ofnickel 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The opening ratiocan be appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

Hereinbelow, one aspect of the electrode for electrolysis in the presentembodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 68, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also shown in FIG. 68, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 68, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol or the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Tr, Pt, Au,Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, andLu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The curabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Tm, Yb, andLu, and oxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thicknesspreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis is measured in the same manner as thethickness of the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

In the present embodiment, the electrode for electrolysis preferablycontains at least one catalytic component selected from the groupconsisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O,Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy from the viewpointof achieving sufficient electrolytic performance.

In the present embodiment, from the viewpoint that the electrode forelectrolysis, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a macroporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness or 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking or a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst layer is formedon the substrate for electrode for electrolysis by an application stepof applying a coating liquid containing a catalyst, a drying step ofdrying the coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysis isperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 obtained by applying a solution in which metal saltsof various combination are dissolved (first coating liquid) onto thesubstrate for electrode for electrolysis and then pyrolyzing (baking)the coating liquid in the presence of oxygen. The content of the metalin the first coating liquid is substantially equivalent to that in thefirst layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/m inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and the further post-bakedfor a long period as required can further improve the stability of thefirst layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating. An exampleincludes a method in which the substrate is fixed in a chamber and themetal ruthenium target is irradiated with an electron beam. Evaporatedmetal ruthenium particles are positively charged in plasma in thechamber to deposit on the substrate negatively charged. The plasmaatmosphere is argon and oxygen, and ruthenium deposits as rutheniumoxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

The electrode for electrolysis in the present embodiment can beintegrated with a membrane such as an ion exchange membrane and amicroporous membrane and used. Thus, the laminate in the presentembodiment can be used as a membrane-integrated electrode. Then, thesubstituting work for the cathode and anode on renewing the electrode iseliminated, and the work efficiency is markedly improved.

The electrode integrated with the membrane such as an ion exchangemembrane and a microporous membrane can make the electrolyticperformance comparable to or higher than those of a new electrode.

Hereinafter, the ion exchange membrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane is not particularly limited as long as themembrane can be laminated with the electrode for electrolysis, andvarious ion exchange membranes may be employed. In the presentembodiment, an ion exchange membrane that has a membrane body containinga hydrocarbon polymer or fluorine-containing polymer having an ionexchange group and a coating layer provided on at least one surface ofthe membrane body is preferably used. It is preferable that the coatinglayer contain inorganic material particles and a binder and the specificsurface area of the coating layer be 0.1 to 10 m²/g. The ion exchangemembrane having such a structure has a small influence of gas generatedduring electrolysis on electrolytic performance and tends to exertstable electrolytic performance.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO₃—, hereinbelow also referred to as a “sulfonicacid group” or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂—, hereinbelowalso referred to as a “carboxylic acid group”). From the viewpoint ofstrength and dimension stability, reinforcement core materials arepreferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 69 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containingpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group (a group represented by—CO₂—, hereinbelow also referred to as a “carboxylic acid group”), andthe reinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane 1, as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, is suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 69.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)_(s)—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time or hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having, a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0.5 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane 1, a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer located on the anode side of theelectrolyzer and the carboxylic acid layer 2 located on the cathode sideof the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane preferably has a coating layer on at least onesurface of the membrane body. As shown in FIG. 69, in the ion exchangemembrane 1, coating layers 11 a and 11 b are formed on both the surfacesof the membrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides or Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durability, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurities suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contract the ion exchange membrane can be controlled inthe desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, alkalis, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PEA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) is preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area or surface through which substances such as ions(an electrolyte solution and cations contained therein (e.g., sodiumions)) can pass (B) to the area of either one surface of the membranebody (A) (B/A). The total area of the surface through which substancessuch as ions can pass (B) can refer to the total areas of regions inwhich in the ion exchange membrane, cations, an electrolytic solution,and the like are not blocked by the reinforcement core materials and thelike contained in the ion exchange membrane.

FIG. 70 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 70, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapeof sacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step (4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include(i) a method in which a fluorine-containing polymer having a carboxylicacid group precursor (e.g., carboxylate functional group) (hereinafter,a layer comprising the same is referred to as the first layer) locatedon the cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using, aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property capable sufficiently retaining themechanical strength the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing, polymer having a carboxylic acid group precursorand a fluorine-containing polymer having a sulfonic acid group precursorare separately produced and then mixed or may be a method in which amonomer having a carboxylic acid group precursor and a monomer having asulfonic acid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing, material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that is, projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 71(a) and (b) are schematic viewsfor explaining a method for forming the continuous holes of the ionexchange membrane.

FIGS. 71(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 71(a) exemplifies the plain-woven reinforcing material in which thereinforcement yarns 52 and sacrifice yarns 504 a are interwoven alongboth the longitudinal direction and the lateral direction in the paper,and the arrangement of the reinforcement yarns 52 and the sacrificeyarns 504 a in the reinforcing material may be varied as required.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counterion of the ion exchange group by (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example, and ispreferably 30 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

In the present embodiment, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having an EW(ion exchange capacity) different from that of the first ion exchangeresin layer. Additionally, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having afunctional group different from that of the first on exchange resinlayer. The ion exchange capacity can be adjusted by the functional groupto be introduced, and functional groups that may be introduced are asmentioned above.

In the present embodiment, the portion of the laminate 25 to besandwiched between the anode gasket 12 and the cathode gasket 13 ispreferably a non-conducting surface. The “conducting surface”corresponds to a portion designed so as to allow electrolytes to migratebetween the anode chamber and the cathode chamber, and the“non-conducting surface” is a portion not corresponding to theconducting surface.

In the present embodiment, the outermost perimeter of the laminate maybe located on a more inner side or farther outside than the outermostperimeter of the anode side gasket and the cathode side gasket in thedirection of the conducting surface, but is preferably located fartheroutside. In the case of such a configuration, the outermost perimeterlocated farther outside can be used as a grip margin, and thus, theworkability on assembling the electrolyzer tends to be improved. Theoutermost perimeter of the laminate herein is the outermost perimeter ofthe membrane and the electrode for electrolysis in combination. That is,when the outermost perimeter of the electrode for electrolysis islocated farther outside of the mutual contact surface than the outermostperimeter of the membrane, the outermost perimeter of the laminate meansthe outermost perimeter of the electrode for electrolysis. In contrast,when the outermost perimeter of the electrode for electrolysis islocated on a more inner side of the mutual contact surface than theoutermost perimeter of the membrane, the outermost perimeter of thelaminate means the outermost perimeter of the membrane.

The positional relation will be described by use of FIGS. 72 and 73.FIGS. 72 and 73 particularly show the positional relation of the gasketsand the laminate when the two electrolytic in shown in FIG. 64B, forexample, are observed from the α-direction. In FIGS. 72 and 73, arectangular gasket A having an aperture portion at the center is locatedat the most front side. A rectangular membrane B is located at the backof A, and a rectangular electrode for electrolysis C is further locatedat the back of B. That is, the aperture portion of the gasket A is aportion corresponding to the conducting surface of the laminate.

In FIG. 72, the outermost perimeter A1 of the gasket A is located on amore inner side than the outermost perimeter B1 of the membrane B andthe outermost perimeter C1 of the electrode for electrolysis C in thedirection of the conducting surface.

In FIG. 73, the outermost perimeter A1 of the gasket A is locatedfarther outs than the outermost perimeter C1 of the electrode forelectrolysis C in the direction of the conducting surface, but theoutermost perimeter B1 of the membrane B is located farther outside thanthe outermost perimeter A1 of the gasket A in the direction of theconducting surface.

In the present embodiment, the laminate should be sandwiched between theanode side gasket and the cathode side gasket, and the electrode forelectrolysis per se may not be sandwiched directly between the anodeside gasket and the cathode side gasket. That is, as long as theelectrode for electrolysis per se is fixed to the membrane, only themembrane may be sandwiched directly between the anode side gasket andthe cathode side gasket. In the present embodiment, from the viewpointof more stably fixing the electrode for electrolysis in theelectrolyzer, both the electrode for electrolysis and the membrane arepreferably sandwiched between the anode side gasket and the cathode sidegasket.

In the present embodiment, the membrane and the electrode forelectrolysis are fixed by at least the anode gasket and the cathodegasket to exist as a laminate, but may take other fixing configuration.For example, a fixing configuration exemplified below may be employed.Only one fixing configuration can be employed, or two or more fixingconfigurations can be employed in combination.

In the present embodiment, at least a portion of the electrode forelectrolysis preferably penetrates the membrane and thereby is fixed.The aspect will be described by use of FIG. 74A.

In FIG. 74A, at least a portion of the electrode for electrolysis 2penetrates the membrane 3 and thereby is fixed. FIG. 74A shows anexample in which the electrode for electrolysis 2 is a metal porouselectrode. That is, in FIG. 74A, a plurality of portions of theelectrode for electrolysis 2 are separately shown, but these portionsare continuous. Thus, the cross-section of an integral metal porouselectrode is shown (the same apples to FIGS. 75 to 78 below).

In the electrode configuration, when the membrane 3 in the predeterminedposition (position to be the fixed portion), for example, is pressedonto the electrode for electrolysis 2, a portion of the membrane 3intrudes into the asperity geometry or opening geometry on the surfaceof the electrode for electrolysis 2. Then, recesses on the electrodesurface and projections around openings penetrate the membrane 3 andpreferably penetrate through to the outer surface 3 b of the membrane 3,as shown in FIG. 74A.

As described above, the fixing configuration in FIG. 74A can be producedby pressing the membrane 3 onto the electrode for electrolysis 2. Inthis case, the membrane 3 is softened by warming and then subjected tothermal compression and thermal suction. Then, the electrode forelectrolysis 2 penetrates the membrane 3. Alternatvely, the membrane 3may be used in a melt state. In this case, the membrane is preferablysuctioned from the side of the outer surface 2 b (back surface side) ofthe electrode for electrolysis 2 in the state shown in FIG. 74B. Theregion in which the membrane 3 is pressed onto the electrode forelectrolysis 2 constitutes the “fixed portion”.

The fixing configuration shown in FIG. 74A can be observed by amagnifier (loupe), optical microscope, or electron microscope. Since theelectrode for electrolysis 2 has penetrated the membrane 3, it ispossible to estimate the fixing configuration in FIG. 74A by a test ofthe conduction between the outer surface 3 b of the membrane 3 and theouter surface 2 b of the electrode for electrolysis 2 by use of a testeror the like.

In the present embodiment, at least a portion of the electrode forelectrolysis is located and fixed inside the membrane in the fixedportion. The aspect will be described by use of FIG. 75A.

As described above, the surface of the electrode for electrolysis 2 hasan asperity geometry or opening geometry. In the embodiment shown inFIG. 75A, a portion of the electrode surface enters the membrane 3 inthe predetermined position (position to be the fixed portion) and isfixed thereto. The configuration shown in FIG. 75A can be produced bypressing the membrane 3 onto the electrode for electrolysis 2. In thiscase, the fixing configuration in FIG. 75A is preferably formed bysoftening the membrane 3 by warming and then thermally compressing andthermally suctioning the membrane 3. Alternatively, the fixingconfiguration in FIG. 75A can be formed by melting the membrane 3. Inthis case, the membrane 3 is preferably suctioned from the side of theouter surface 2 b (back surface side) of the electrode for electrolysis2.

The fixing configuration shown in FIG. 75A can be observed by amagnifier (loupe), optical microscope, or electron microscope.Particularly preferable is a method including subjecting the sample toan embedding treatment, then forming a cross-section by a microtome, andobserving the cross-section. In the fixing configuration shown in FIG.75A, the electrode for electrolysis 2 does not penetrate the membrane 3.Thus, no conduction between the outer surface 3 b of the membrane 3 andthe outer surface 2 b of the electrode for electrolysis 2 is identifiedby the conduction test.

In the present embodiment, it is preferable that the laminate furtherhave a fixing member for fixing the membrane and the electrode forelectrolysis. The aspect will be described by use of FIGS. 76A to C.

The fixing configuration shown FIG. 76A is a configuration in which afixing member 7, which is separate from the electrode for electrolysis 2and the membrane 3, is used and the fixing member 7 penetrates andthereby fixes the electrode for electrolysis 2 and the membrane 3. Theelectrode for electrolysis 2 is not necessarily penetrated by the fixingmember 7, and should be fixed by the fixing member 7 so as not to beseparated from the membrane 2. The material for the fixing member 7 isnot particularly limited, and materials constituted by metal, resin, orthe like, for example, can be used as the fixing member 7. Examples ofthe metal include nickel, nichrome, titanium, and stainless steel (SUS).Oxides thereof may be used. Examples of the resin that can be usedinclude fluorine resins (e.g., polytetrafluoroethylene (PTFE),copolymers of tetrafluoroethylene and perfluoroalkoxy ethylene (PFA),copolymers of tetrafluoroethylene and ethylene (ETFE), materials for themembrane 3 described below), polyvinylidene fluoride (PVDF),ethylene-propylene-diene rubber (EPDM), polyethylene (PP), polypropylene(PE), nylon, and aramid.

In the present embodiment, for example, a yarn-like metal or resin isused to sew the predetermined position (position to be the fixedportion) between the outer surface 2 b of the electrode for electrolysis2 and the outer surface 3 b of the membrane 3, as shown in FIGS. 76B andC. It is also possible to fix the electrode for electrolysis 2 to themembrane 3 by use of a fixing mechanism such as a tucker.

The fixing configuration shown in FIG. 77 is a configuration in whichfixing is made by an organic resin (adhesion layer) interposed betweenthe electrode for electrolysis 2 and the membrane 3. That is, in FIG.77, shown is a configuration in which an organic resin as the fixingmember 7 is arranged on the predetermined position (position to be thefixed portion) between the electrode for electrolysis 2 and the membrane3 to thereby make fixing by adhesion. For example, the organic resin isapplied onto the inner surface 2 a of the electrode for electrolysis 2,the inner surface 3 a of the membrane 3, or one or both of the innersurface 2 a of the electrode for electrolysis 2 and the inner surface 3a of the membrane 3. Then, the fixing configuration shown in FIG. 77 canbe formed by laminating the electrode for electrolysis 2 to the membrane3. The materials for the organic resin are not particularly limited, butexamples thereof that can be used include fluorine resins (e.g., PTFE,PFE, and PFPE) and resins similar the materials constituting themembrane 3 as mentioned above. Commercially availablefluorine-containing adhesives and PTFE dispersions also can be used asappropriate. Additionally, multi-purpose vinyl acetate adhesives,ethylene-vinyl acetate copolymer adhesives, acrylic resin adhesives,α-olefin adhesives, styrene-butadiene rubber latex adhesives, vinylchloride resin adhesives, chloroprene adhesives, nitrile rubberadhesives, urethane rubber adhesives, epoxy adhesives, silicone resinadhesives, modified silicone adhesives, epoxy-modified silicone resinadhesives, silylated urethane resin adhesives, cyanoacrylate adhesives,and the like also can be used.

In the present embodiment, organic resins that dissolve in anelectrolyte solution or dissolve or decompose during electrolysis may beused. Examples of the resins that dissolve in an electrolyte solution ordissolve or decompose during electrolysis include, but are not limitedto, vinyl acetate adhesives, ethylene-vinyl acetate copolymer adhesives,acrylic resin adhesives, α-olefin adhesives, styrene-butadiene rubberlatex adhesives, vinyl chloride resin adhesives, chloroprene adhesives,nitrile rubber adhesives, urethane rubber adhesives, epoxy adhesives,silicone resin adhesives, modified silicone adhesives, epoxy-modifiedsilicone resin adhesives, silylated urethane resin adhesives, andcyanoacrylate adhesives.

The fixing configuration shown in FIG. 77 can be observed by an opticalmicroscope or electron microscope. Particularly preferable is a methodincluding subjecting the sample to an embedding treatment, then forminga cross-section by a microtome, and observing the cross-section.

In the present embodiment, at least a portion of the fixing memberpreferably externally grips the membrane and the electrode forelectrolysis. The aspect will be described by use of FIG. 78A.

The fixing configuration shown in FIG. 78A is a configuration in whichthe electrode for electrolysis 2 and membrane 3 are externally grippedand fixed. That is, the outer surface 2 b of the electrode forelectrolysis 2 and the outer surface 3 b of the membrane 3 aresandwiched and fixed by a gripping member as the fixing member 7. In thefixing configuration shown in FIG. 78A, a state in which the grippingmember is engaging in the electrode for electrolysis 2 and the membrane3 is also included. Examples of the gripping member include tape andclips.

In the present embodiment, a gripping member that dissolves in anelectrolyte solution may be used. Examples of the gripping member thatdissolves in an electrolyte solution include PET tape and clips and PVAtape and clips.

In the fixing configuration shown in FIG. 78A, unlike those in FIGS. 74to FIG. 77, the electrode for electrolysis 2 and the membrane 3 are notbonded at the interface therebetween, but the inner surface 2 a of theelectrode for electrolysis 2 and the inner surface 3 a of the membrane 3are only abutted or opposed to each other. Removal of the grippingmember can release the fixed state of the electrode for electrolysis 2and the membrane 3 and separate the electrode for electrolysis 2 fromthe membrane 3.

Although not shown in FIG. 78A, it is also possible to fix the electrodefor electrolysis 2 and the membrane 3 using a gripping, member in anelectrolytic cell.

Also in the present embodiment, at least a portion of the fixing memberpreferably fixes the membrane and the electrode for electrolysis bymagnetic force. The aspect will be described by use of FIG. 78B.

The fixing configuration shown in FIG. 78B is a configuration in whichthe electrode for electrolysis 2 and membrane 3 are externally grippedand fixed. The difference from that in FIG. 78A is that a pair ofmagnets are used as the gripping member, which is the fixing member. Inthe aspect of the fixing configuration shown in FIG. 78B, a laminate 1is attached to the electrolyzer. Thereafter, during operation of theelectrolyzer, the gripping member may be left as it is or may be removedfrom the laminate 1.

Although not shown in FIG. 78B, it is also possible to fix the electrodefor electrolysis 2 and the membrane 3 using a gripping member in anelectrolytic cell. When a magnetic material that adheres to magnets isused as a part of the mater al for the electrolytic cell, one grippingmaterial is placed on the side of the membrane surface. Then, thegripping material and the electrolytic cell can sandwich and fix theelectrode for electrolysis 2 and the membrane 3 therebetween.

A plurality of fixed portion lines can be provided. That is, 1, 2, 3, .. . n fixed portion lines can be arranged from the side f the contourtoward the inner side of the laminate 1. n is an integer of 1 or more.The m-th (m<n) fixed portion line and the L-th (m<L≤n) fixed portionline can be each formed to have a different fixation pattern.

A fixed portion line to be formed in the conducting surface preferablyhas a line-symmetric shape. This tends to enable stress concentration tobe controlled. For example, when two orthogonally intersectingdirections are referred to as the X direction and the Y direction, it ispossible to configure the fixed portion by arranging a fixed portionline each in the X direction and the Y direction or arranging aplurality of fixed portion lines at equal intervals each in the Xdirection and the Y direction. The number of fixed portion lines each inthe X direction and the Y direction is not limited, but is preferably100 or less each in the X direction and the Y direction. From theviewpoint of achieving the planarity of conducting surface, the numberof fixed portion lines is preferably 50 or less each in the X directionand the Y direction.

When the fixed portion in the present embodiment has the fixingconfiguration shown in FIG. 74A or FIG. 76, a sealing material ispreferably applied onto the membrane surface of the fixed portion fromthe viewpoint of preventing a short circuit caused by a contact betweenthe anode and the cathode. As the sealing material, the materialsdescribed for the above adhesives can be used.

The laminate in the present embodiment may have various fixed portionsin various positions as mentioned above, but from the viewpoint ofsufficiently achieving electrolytic performance, these fixed portionsare preferably present on the non-conducting surface.

The laminate in the present embodiment may have various fixed portionsin various positions as mentioned above, but the electrode forelectrolysis preferably satisfies the “force applied” mentioned aboveparticularly in a portion in which no fixed portion is present(non-fixed portion). That is, the force applied per unit·mass unit areaof the electrode for electrolysis in the non-fixed portion is preferablyless than 1.5 N/mg·cm².

In the present embodiment, it is preferable that the membrane comprisean ion exchange membrane comprising a surface layer containing anorganic resin and the electrode for electrolysis be fixed by the organicresin. The organic resin is as mentioned above and can be formed as thesurface layer of the ion exchange membrane by various known methods.

(Water Electrolysis)

The electrolyzer of the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

(Method for Producing Electrolyzer and Method for Renewing Laminate)

A method for renewing the laminate in the electrolyzer of the presentembodiment has a step of separating the laminate in the presentembodiment from the anode side gasket and the cathode side gasket tothereby remove the laminate out of the electrolyzer, and a step ofsandwiching a new laminate between the anode side gasket and the cathodeside gasket. The new laminate means the laminate in the presentembodiment, and at least one of the electrode for electrolysis and themembrane should be new.

In the step of sandwiching the laminate described above, from theviewpoint of more stably fixing the electrode for electrolysis in theelectrolyzer, both the electrode for electrolysis and the membrane arepreferably sandwiched between the anode side gasket and the cathode sidegasket.

Additionally, the method for producing the electrolyzer of the presentembodiment has a step of sandwiching the laminate in the presentembodiment between the anode side gasket and the cathode side gasket.

The method for producing the electrolyzer and method for renewing thelaminate of the present embodiment, as configured as described above,can improve the work efficiency during electrode renewing in theelectrolyzer and further can provide excellent electrolytic performancealso after renewing.

Also in the step of sandwiching the laminate described above, from theviewpoint of more stably fixing the electrode for electrolysis in theelectrolyzer, both the electrode for electrolysis and the membrane arepreferably sandwiched between the anode side gasket and the cathode sidegasket.

Fifth Embodiment

Here, a fifth embodiment of the present invention will be described indetail with reference to FIGS. 91 to 102.

[Method for Producing Electrolyzer]

The method for producing an electrolyzer according to the fifthembodiment (hereinafter, in the section of <Fifth embodiment>, simplyreferred to as “the present embodiment”) is a method for producing a newelectrolyzer by arranging an electrode for electrolysis or a laminate ofthe electrode for electrolysis and a new membrane in an existingelectrolyzer comprising an anode, a cathode that is opposed to theanode, and a membrane that is arranged between the anode and thecathode, wherein the electrode for electrolysis or the laminate, beingin a wound body form, is used. As described above, according to themethod for producing an electrolyzer in accordance with the presentembodiment, an electrode for electrolysis or a laminate of the electrodefor electrolysis and a new membrane, being in a wound body form, isused. Thus, the electrode for electrolysis or the laminate when used asa member of the electrolyzer can be downsized for transport or the like,and the work efficiency during electrode renewing in the electrolyzercan be improved.

In the present embodiment, the existing electrolyzer comprises an anode,a cathode that is opposed to the anode, and a membrane that is arrangedbetween the anode and the cathode as constituent members, in otherwords, comprises an electrolytic cell. The existing electrolyzer is notparticularly limited as long as comprising the constituent membersdescribed above, and various known configurations may be employed.

In the present embodiment, a new electrolyzer further comprises anelectrode for electrolysis or a laminate, in addition to a member thathas already served as the anode or cathode in the existing electrolyzer.That is, the “electrode for electrolysis” arranged on production of anew electrolyzer serves as the anode or cathode, and is separate fromthe cathode and anode in the existing electrolyzer. In the presentembodiment, even in the case where the electrolytic performance of theanode and/or cathode has deteriorated in association with operation ofthe existing electrolyzer, arrangement of an electrode for electrolysisseparate therefrom enables the characteristics of the anode and/orcathode to be renewed. In the case where a laminate is used in thepresent embodiment, a new ion exchange membrane is arranged incombination, and thus, the characteristics of the ion exchange membrane,which have deteriorated in association with operation, can be renewedsimultaneously.

“Renewing the characteristics” referred to herein means to havecharacteristics comparable to the initial characteristics possessed bythe existing electrolyzer before being operated or to havecharacteristics higher than the initial characteristics.

In the present embodiment, the existing electrolyzer is assumed to be an“electrolyzer that has been already operated”, and the new electrolyzeris assumed to be an “electrolyzer that has not been yet operated”. Thatis, once an electrolyzer produced as a new electrolyzer is operated, theelectrolyzer becomes “the existing electrolyzer in the presentembodiment”. Arrangement of an electrode for electrolysis or a laminatein this existing electrolyzer provides “a new electrolyzer of thepresent embodiment”.

Hereinafter, a case of performing common salt electrolysis by using anion exchange membrane as the membrane is taken as an example, and oneembodiment of the electrolyzer will be described in detail. In thesection of <Fifth embodiment>, unless otherwise specified, “theelectrolyzer the present embodiment” incorporates both “the existingelectrolyzer in the present embodiment” and “the new electrolyzer in thepresent embodiment”.

[Electrolytic Cell]

First, the electrolytic cell, which can be used as a constituent unit ofthe electrolyzer in the present embodiment, will be described. FIG. 91illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required theelectrolytic cell 1 has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 95, and the cathode 21 and the reverse currentabsorbing layer 18 b are electrically connected. The cathode chamber 20further has a collector 23, a support 24 supporting the collector, and ametal elastic body 22. The metal elastic body 22 placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer may be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support the support 24 and the collector 23, and the collector 23and the metal elastic body 22 are each directly attached and the cathode21 is laminated on the metal elastic body 22. Examples of a method fordirectly attaching these constituent members to one another includewelding and the like. Alternatively, the reverse current absorber 18,the cathode 21, and the collector 23 may be collectively referred to asa cathode structure 40.

FIG. 92 illustrates a cross-sectional view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 93 shows an electrolyzer4. FIG. 94 shows a step of assembling the electrolyzer 4.

As shown in FIG. 92, an electrolytic cell 1, a cation exchange membrane2, and an electrolytic cell 1 are arranged in series in the ordermentioned. An ion exchange membrane 2 is arranged between the anodechamber of one electrolytic cell 1 among the two electrolytic cells thatare adjacent in the electrolyzer and the cathode chamber of the otherelectrolytic cell 1. That is, the anode chamber 10 of the electrolyticcell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacentthereto is separated by the cation exchange membrane 2. As shown in FIG.93, the electrolyzer 4 is composed of a plurality of electrolytic cells1 connected in series via the ion exchange membrane 2. That is, theelectrolyzer 4 is a bipolar electrolyzer comprising the plurality ofelectrolytic cells 1 arranged in series and ion exchange membranes 2each arranged between adjacent electrolytic cells 1. As shown in FIG.94, the electrolyzer 4 is assembled by arranging the plurality ofelectrolytic cells 1 in series via the ion exchange membrane 2 andcoupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That is, the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine electrolyzed, chlorine gas is generated on theside of the anode 11, and sodium hydroxide (solute) and hydrogen gas aregenerated on the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Thefeed conductor herein referred to mean a degraded electrode (i.e., theexisting electrode), an electrode having no catalyst coating, and thelike. When the electrode for electrolysis in the present embodiment isinserted to the anode side, 11 serves as an anode feed conductor. Whenthe electrode for electrolysis in the present embodiment is not insertedto the anode side, 11 serves as an anode. The anode chamber 10preferably has an anode-side electrolyte solution supply unit thatsupplies an electrolyte solution to the anode chamber 10, a baffle platethat is arranged above the anode-side electrolyte solution supply unitso as to be substantially parallel or oblique to a partition wall 30,and an anode-side gas liquid separation unit that is arranged above thebaffle plate to separate gas from the electrolyte solution including thegas mixed.

(Anode)

When the electrode for electrolysis in the present embodiment is notinserted to the anode side, an anode 11 is provided in the frame of theanode chamber 10 (i.e., the anode frame). As the anode 11, a metalelectrode such as so-called DSA(R) can be used. DSA is an electrodeincluding a titanium substrate of which surface is covered with an oxidecomprising ruthenium, iridium, and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-called,woven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA having athinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 91,and below means the lower direction in the electrolytic cell 1 in FIG.91.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 in the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 91, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis in thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis in thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis in the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20 (i.e., cathode frame). The cathode 21 preferablyhas a nickel substrate and a catalyst layer that covers the nickelsubstrate. Examples of the components of the catalyst layer on thenickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W,Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.Examples of the method for forming the catalyst layer include plating,alloy plating, dispersion/composite plating, CVD, PVD, pyrolysis, andspraying. These methods may be used in combination. The catalyst layermay have a plurality of layers and a plurality of elements, as required.The cathode 21 may be subjected to a reduction treatment, as required.As the substrate of the cathode 21, nickel, nickel alloys, andnickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mb, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. Nickel, nickel alloys, andnickel-plated iron or stainless, having no catalyst coating may be used.As the substrate of the cathode feed conductor 21, nickel, nickelalloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electrolytic cells 1 connected in series. Lowering thevoltage enables the power consumption to be reduced. With the metalelastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis in the present embodiment is placed in the electrolyticcell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantially perpendicular to thepartition wall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane (see FIG. 92). These gaskets can impart airtightness toconnecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced gas and be usable for a long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (PPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 92), each electrolytic cell 1 onto which the gasketis attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

[Step of Using Wound Body]

The wound body in the present embodiment may be the electrode forelectrolysis being in a wound body form, or may be a laminate of theelectrode for electrolysis and a new membrane, being in a wound bodyform. In the method for producing an electrolyzer according to thepresent embodiment, the wound body is used. Specific examples of thestep of using a wound body include, but are not limited thereto, includea method in which, first in the existing electrolyzer, a fixed state ofthe adjacent electrolytic cell and ion exchange membrane by means of apress device is released to provide a gap between the electrolytic celland the ion exchange membrane, then, an electrode for electrolysis beingin a wound body form, after its wound state is released, is insertedinto the gap, and the members are coupled again by means of the pressdevice. In the case where the laminate being in a wound body form isused, examples of the method include a method in which, after a gap isformed between the electrolytic cell and the ion exchange membrane asdescribed above, the existing ion exchange membrane to be renewed isremoved, then, a laminate being in a wound body form, after its woundstate is released, is inserted into the gap, and the members are coupledagain by means of the press device. By means the method, an electrodefor electrolysis or laminate can be arranged on the surface of the anodeor the cathode of the existing electro and the characteristics of theion exchange membrane and the anode and/or cathode can be renewed.

As described above, in the present embodiment, the step of using a woundbody preferably has a step (B) of releasing the wound state of a woundbody, and after the step (B), more preferably has a step (C) ofarranging an electrode for electrolysis or laminate on the surface of atleast one of the anode and the cathode.

In the present embodiment, the step of using a wound body preferably hasa step of retaining the electrode for electrolysis or laminate in awound state to thereby obtain a wound body. In the step (A), theelectrode for electrolysis or laminate per se may be wound to form awound body, or the electrode for electrolysis or laminate may be woundaround a core to form a wound body. As the core that may be used here,which is not particularly limited, a member having a substantiallycylindrical form and having a size corresponding to the electrode forelectrolysis or laminate can be used, for example.

[Electrode for Electrolysis]

In the present embodiment, the electrode for electrolysis is notparticularly limited as long as the electrode is used as a wound body asmentioned above, that is, is woundable. The electrode for electrolysismay be an electrode that serves as the cathode in the electrolyzer ormay be an electrode that serves as an anode. As the material, form, andthe like of the electrode for electrolysis, those suitable for forming awound body may be appropriately selected, in consideration of the stepof using a wound body, the configuration of the electrolyzer, and thelike in the present embodiment. Hereinbelow, preferable aspects of theelectrode for electrolysis in the present embodiment will be described,but these are merely exemplary aspects preferable for forming a woundbody. Electrodes for electrolysis other than the aspects mentioned belowcan be appropriately employed.

The electrode for electrolysis in the present embodiment has a forceapplied per unit mass·unit area of preferably 1.6 N/(mg·cm²) or less,more preferably less than 1.6 N/(mg·cm²), further preferably less than1.5 N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less from the viewpoint of enabling a goodhandling property to be provided and having a good adhesive force to amembrane such as an ion exchange membrane and a macroporous membrane, afeed conductor (a degraded electrode and an electrode having no catalystcoating), and the like. The force applied is even still more preferably1 N/mg·cm² or less, further still more preferably 1.10 N/mg·cm² or less,particularly preferably 1.0 N/mg·cm² or less, especially preferably 1.00N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0. 2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit is preferably 48 mg/cm² or less, more preferably 30mg/cm² or less, further preferably 20 mg/cm² or less from the viewpointof enabling a good handling property to be provided, having a goodadhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and of economy, and furthermore is preferably 15mg/cm² or less from the comprehensive viewpoint including handlingproperty, adhesion, and economy. The lower limit value is notparticularly limited but is of the order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as detailed in Examples. As for the force applied, thevalue obtained by the measurement of the method (i) (also referred to as“the force applied (1)”) and the value obtained by the measurement ofthe method (ii) (also referred to as “the force applied (2)”) may be thesame or different, and either of the values preferably less than 1.5N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode (130 mm square) are laminated in this order.After this laminate is sufficiently immersed in pure water, excess waterdeposited on the surface of the laminate is removed to obtain a samplefor measurement. The arithmetic average surface roughness (Ra) of thenickel plate after the blast treatment is 0.5 to 0.8 μm. The specificmethod for calculating the arithmetic average surface roughness (Ra) isas described in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method (i)is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. The force ispreferably more than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and furthermore, isfurther more preferably 0.14 N/(mg·cm²), still more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m.).

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method. (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurement. Under conditionsof a temperature of 23±2° C. and a relative humidity of 30±5%, only thesample of electrode in this sample for measurement is raised in avertical direction at 10 mm/minute using a tensile and compressiontesting machine, and the load when the sample of electrode is raised by10 mm in a vertical direction is measured. This measurement is repeatedthree times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. Further, the forceis preferably more than 0.005 N/(mg·cm²), more preferably 0.02N/(mg·cm²) or more, further preferably 0.1 N/(mg·cm²) or more from theviewpoint of further improving the electrolytic performance, and isfurther more preferably 0.14 N/(mg·cm²) or more from the viewpoint offurther facilitating handling in a large size (e.g., a size of 1.5 m×2.5m).

The electrode for electrolysis in the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 120 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, being capable or being suitably rolled in aroll and satisfactorily folded, and facilitating, handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 more preferably 15 μm.

The proportion measured by the following method (2) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint of further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2) ]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The electrode for electrolysis in the present embodiment preferably has,but is not particularly limited to, a porous structure and an openingratio or void ratio of 5 to 90% or less, from the viewpoint of enablinga good handling property to be provided, having a good adhesive force toa membrane such as an ion exchange membrane and a microporous membrane,a degraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, and preventing accumulation of gas to begenerated during electrolysis. The opening ratio is more preferably 10to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V is calculated fromthe values of the gauge thickness, width, and length of electrode, andfurther, a weight W is measured to thereby enable an opening ratio A tobe calculated by the following formula.

A=(1−(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio can be appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

Hereinbelow, a more specific embodiment of the electrode forelectrolysis in the present embodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 96, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also shown in FIG. 96, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 96, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol of the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium +neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may he added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The durabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Yb, andLu, and oxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff the substrate. The thickness is more preferably 0.05 μm to 15 μm.The thickness is more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thickness ispreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis is measured in the same manner as thethickness the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

In the present embodiment, the electrode for electrolysis preferablycontains at least one catalytic component selected from the groupconsisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O,Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy from the viewpointof achieving sufficient electrolytic performance.

In the present embodiment, from the viewpoint that the electrode forelectrolysis, if being an electrode having a broad elastic deformationregion can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness of 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking of a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst layer is formedon the substrate for electrode for electrolysis by an application stepof applying a coating liquid containing a catalyst, a drying step ofdrying the coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysis isperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and the further post-bakedfor a long period as required can further improve the stability of thefirst layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 is obtained by applying a solution in which metalsalts of various combination are dissolved (first coating liquid) ontothe substrate for electrode for electrolysis and then pyrolyzing(baking) the coating liquid in the presence of oxygen. The content ofthe metal in the first coating liquid is substantially equivalent tothat in the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 0° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating. An exampleincludes a method in which the substrate is fixed in a chamber and themetal ruthenium target is irradiated with an electron beam. Evaporatedmetal ruthenium particles are positively charged in plasma in thechamber to deposit on the substrate negatively charged. The plasmaatmosphere is argon and oxygen, and ruthenium deposits as rutheniumoxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

[Laminate]

The electrode for electrolysis in the present embodiment can be combinedwith a membrane such as an ion exchange membrane or a microporousmembrane and used as a laminate. That is, the laminate in the presentembodiment comprises the electrode for electrolysis and a new membrane.The new membrane is not particularly limited as long as being separatefrom the membrane in the existing electrolyzer, and various known“membranes” can be used. The material, form, physical properties, andthe like of the new membrane may be similar to those of the membrane inthe existing electrolyzer.

Hereinafter, an ion exchange membrane according to one aspect of themembrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane is not particularly limited as long as themembrane can be laminated with the electrode for electrolysis, andvarious ion exchange membranes may be employed. In the presentembodiment, an ion exchange membrane that has a membrane body containinga hydrocarbon polymer or fluorine-containing polymer having an ionexchange group and a coating layer provided on at least one surface ofthe membrane body is preferably used. It is preferable that the coatinglayer contain inorganic material particles and a binder and the specificsurface area of the coating layer be 0.1 to 10 m²/g. The ion exchangemembrane having such a structure has a small influence of gas generatedduring electrolysis on electrolytic performance and tends to exertstable electrolytic performance.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO—, hereinbelow also referred to as a “sulfonicacid group”) or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂—, hereinbelowalso referred to as a “carboxylic acid group”). From the viewpoint ofstrength and dimension stability, reinforcement core materials arepreferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 97 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containingpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by —SO₃—, hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group (a group represented by—CO₂—, hereinbelow also referred to as a “carboxylic acid group”), andthe reinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, is suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 97.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing, polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)₂—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time of hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0.5 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer 2 is located on the cathodeside of the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatthe carboxylic acid layer 2 from the viewpoint of membrane strength. Themembrane thickness of the sulfonic acid layer 3 is preferably 2 to 25times, more preferably 3 to 15 times that of the carboxylic acid layer2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained, by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane preferably has a coating layer on at least onesurface of the membrane body. As shown in FIG. 97, in the ion exchangemembrane 1, coating layers 11 a and 11 b are formed on both the surfacesof the membrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides of Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durabilty, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurites suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing acidfluorine-containing polymer having a carboxylic acid group (carboxylicacid layer), a fluorine-containing polymer having a carboxylic acidgroup is further preferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contraction of the ion exchange membrane can be controlledin the desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more prof crab 50 to 250 deniers. The weave density (fabriccount per unit length) preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area of a surface through which substances such asions (an electrolyte solution and cations contained therein sodiumions)) can pass (B) to the area of either one surface of the membranebody (A) (B/A). The total area of the surface through which substancessuch as ions can pass (B) can refer to the total areas of regions inwhich in the ion exchange membrane, cations, an electrolytic solution,and the like are not blocked by the reinforcement core materials and thelike contained in the ion exchange membrane.

FIG. 98 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 98, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes not particularly limited, but may be the shape ofsacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step(4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based, on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand, comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include(i) a method in which a fluorine-containing polymer having a carboxylicacid group precursor (e.g., carboxylate functional group) (hereinafter,a layer comprising the same is referred to as the first layer) locatedon the cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property of sufficiently retaining the mechanicalstrength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that is, projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains NON of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably, 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 99(a) and (b) are schematic viewsfor explaining a method for forming the continuous holes of the ionexchange membrane.

FIGS. 99(a) and (b) show reinforcement yarns 52 sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 99(a) exemplifies the plain-woven reinforcing material in which thereinforcement yarns 52 and sacrifice yarns 504 a are interwoven alongboth the longitudinal direction and the lateral direction in the paper,and the arrangement of the reinforcement yarns 52 and the sacrificeyarns 504 a in the reinforcing material may be varied as required.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counterion of the ion exchange group by H+ (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are Preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particular limited, but can be 20 to 90, for example and preferably30 to 85. The above porosity can be calculated by the following formula:

Porosity (1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

In the present embodiment, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having an EW(ion exchange capacity) different from that of the first ion exchangeresin layer. Additionally, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having afunctional group different from that of the first ion exchange resinlayer. The ion exchange capacity can be adjusted by the functional groupto be introduced, and functional groups that may be introduced are asmentioned above.

(Water Electrolysis)

The electrolyzer in the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

[Method for Renewing Electrode]

The method for producing an electrolyzer according to the presentembodiment can be performed also as a method for renewing an electrode(anode and/or cathode). That is, the method for renewing an electrodeaccording to the present embodiment is a method for renewing an existingelectrode by using an electrode for electrolysis, wherein the electrodefor electrolysis being in a wound body form is used.

Specific examples of a step of using a wound body include, but notparticularly limited to thereto, a method in which the electrode forelectrolysis being in a wound body form, after its wound state isreleased, is arranged on the surface of the existing electrode. By meansof the method, the electrode for electrolysis can be arranged on thesurface of the existing anode or cathode, and the characteristics of theanode and/or cathode can be renewed.

As described above, in the present embodiment, the step of using a woundbody preferably has a step (B′) of releasing the wound state of thewound body, and after the step (B′), more preferably has a step (C′) ofarranging an electrode for electrolysis on the surface of the existingelectrode.

Also in the method for renewing an electrode according to the presentembodiment, the step of using a wound body preferably has a step (A′) ofretaining the electrode for electrolysis in a wound state to therebyobtain a wound body. In the step (A′), the electrode for electrolysisper se may be wound to form a wound body, or the electrode forelectrolysis is wound around a core to form a wound body. As the corethat may be used here, which is not particularly limited, a memberhaving a substantially cylindrical form and having a size correspondingto the electrode for electrolysis can be used, for example.

[Method for Producing Wound Body]

In the method for producing an electrolyzer according to the presentembodiment and the method for renewing an electrode according to thepresent embodiment, the step (A) or (A′), which may be performed, can beperformed also as a method for producing a wound body. That is, themethod for producing a wound body according to the present embodiment isa method for producing a wound body to be used for renewing an existingelectrolyzer comprising an anode, a cathode that is opposed to theanode, and a membrane that is arranged between the anode and thecathode, the method comprising a step of winding an electrode forelectrolysis or a laminate of the electrode for electrolysis and a newmembrane to thereby obtain the wound body. In the step of obtaining awound body, the electrode for electrolysis per se may be wound to form awound body, or the electrode for electrolysis may be wound around a coreto form a wound body. As the core that may be used here, which is notparticularly limited, a member having a substantially cylindrical formand having a size corresponding to the electrode for electrolysis can beused, for example.

Sixth Embodiment

Here, a sixth embodiment of the present invention will be described indetail with reference to FIGS. 103 to 111.

[Method for Producing Electrolyzer]

The method for producing an electrolyzer according to the sixthembodiment (hereinafter, in the section of <Sixth embodiment>, simplyreferred to as “the present embodiment”) is a method for producing a newelectrolyzer by arranging a laminate in an existing electrolyzercomprising an anode, a cathode that is opposed to the anode, and amembrane that is arranged between the anode and the cathode, the methodcomprising a step (A) of integrating an electrode for electrolysis witha new membrane at a temperature at which the membrane does not melt tothereby obtain the laminate, and a step (Ti) of replacing the membranein the existing electrolyzer by the laminate after the step (A).

As described above, according to the method for producing anelectrolyzer according to the present embodiment, it is possible tointegrate and use the electrode for electrolysis and the membrane, notin accordance with an impractical method such as thermal compression.Thus, it is possible to improve the work efficiency during electroderenewing in an electrolyzer.

In the present embodiment, the existing electrolyzer comprises an anode,a cathode that is opposed to the anode, and a membrane that is arrangedbetween the anode and the cathode as constituent members, in otherwords, comprises an electrolytic cell. The existing electrolyzer is notparticularly limited as long as comprising the constituent membersdescribed above, and various known configurations may be employed.

In the present embodiment, a new electrolyzer further comprises anelectrode for electrolysis or a laminate, in addition to a member thathas already served as the anode or cathode in the existing electrolyzer.That is, the “electrode for electrolysis” arranged on production of anew electrolyzer serves as the anode or cathode, and is separate fromthe cathode and anode in the existing electrolyzer. In the presentembodiment, even in the case where the electrolytic performance of theanode and/or cathode has deteriorated in association with operation ofthe existing electrolyzer, arrangement of an electrode for electrolysisseparating therefrom enables the characteristics of the anode and/orcathode to be renewed. Further, a new ion exchange membrane constitutingthe laminate is arranged in combination, and thus, the characteristicsof the ion exchange membrane having characteristics deteriorated inassociation with operation can be renewed simultaneously. “Renewing thecharacteristics” referred to herein means to have characteristicscomparable to the characteristics possessed by the existing electrolyzerbefore being operated or to have characteristics higher than the initialcharacter.

In the present embodiment, the existing electrolyzer is assumed to be an“electrolyzer that has been already operated”, and the new electrolyzeris assumed to be an “electrolyzer that has not been yet operated”. Thatis, once an electrolyzer produced as a new electrolyzer is operated, theelectrolyzer becomes “the existing electrolyzer in the presentembodiment”. Arrangement of an electrode for electrolysis or a laminatein this existing electrolyzer provides “a new electrolyzer of thepresent embodiment”.

Hereinafter, a case of performing common salt electrolysis by using anion exchange membrane as the membrane is taken as an example, and oneembodiment of the electrolyzer will be described in detail. In thesection of <Sixth embodiment>, unless otherwise specified, “theelectrolyze the present embodiment” incorporates both “the existingelectrolyzer in the present embodiment” and “the new electrolyzer in thepresent embodiment”.

[Electrolytic Cell]

First, the electrolytic cell, which can be used as a constituent unit ofthe electrolyzer in the present embodiment, will be described. FIG. 103illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 107, and the cathode 21 and the reverse currentabsorbing layer 18 b are electrically connected. The cathode chamber 20further has a collector 23, a support 24 supporting the collector, and ametal elastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer ma be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support the support 24 and the collector 23, and the collector 23and the metal elastic body 22 are each directly attached and the cathode21 is laminated on the metal elastic body 22. Examples of a method fordirectly attaching these constituent members to one another includewelding and the like. Alternatively, the reverse current absorber 18,the cathode 21, and the collector 23 may be collectively referred to asa cathode structure 40.

FIG. 104 illustrates a cross-section view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 105 shows an electrolyzer4. FIG. 106 shows a step of assembling the electrolyzer

As shown in FIG. 104, an electrolytic cell 1, a cation exchange membrane2, and an electrolytic cell 1 are arranged in series in the ordermentioned. An ion exchange membrane 2 is arranged between the anodechamber of one electrolytic cell 1 among the two electrolytic cells thatare adjacent in the electrolyzer and the cathode chamber of the otherelectrolytic cell 1. That is, the anode chamber 10 of the electrolyticcell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacentthereto is separated by the cation exchange membrane 2. As shown in FIG.105, the electrolyzer 4 is composed of a plurality of electrolytic cells1 connected in series via the ion exchange membrane That is, theelectrolyzer 4 is a bipolar electrolyzer comprising the plurality ofelectrolytic cells 1 arranged in series and ion exchange membranes 2each arranged between adjacent electrolytic cells 1. As shown in FIG.106, the electrolyzer 4 is assembled by arranging the plurality ofelectrolytic cells 1 in series via the ion exchange membrane 2 andcoupling the cells by means of a press device 5.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That is, the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine is electrolyzed, chlorine gas is generated onthe side of the anode 11, and sodium hydroxide (solute) and hydrogen gasare generated on the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Thefeed conductor herein referred to mean a degraded electrode (i.e., theexisting electrode), an electrode having no catalyst coating, and thelike. When the electrode for electrolysis in the present embodiment isinserted to the anode side, 11 serves as an anode feed conductor. Whenthe electrode for electrolysis in the present embodiment is not insertedto the anode side, 11 serves as an anode. The anode chamber 10preferably has an anode-side electrolyte solution supply unit thatsupplies an electrolyte solution to the anode chamber 10, a baffle platethat is arranged above the anode-side electrolyte solution supply unitso as to be substantially parallel or oblique to a partition wall 30,and an anode-side gas liquid separation unit that is arranged above thebaffle plate to separate gas from the electrolyte solution including thegas mixed.

(Anode)

When the electrode for electrolysis in the present embodiment is notinserted to the anode side, an anode 11 is provided in the frame of theanode chamber 10 the anode frame). As the anode 11, a metal electrodesuch as so-called DSA(R) can be used. DSA is an electrode including atitanium substrate of which surface is covered with an oxide comprisingruthenium, iridium, and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to he anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA havingthinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Liquid Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 103,and below means the lower direction in the electrolytic cell 1 in FIG.103.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 in the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 103, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis in thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis in thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 will be not described.

(Cathode)

When the electrode for electrolysis in the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20 (i.e., cathode frame). The cathode 21 preferablyhas a nickel substrate and a catalyst layer that covers the nickelsubstrate. Examples of the components of the catalyst layer on thenickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W,Re, Os, ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.Examples of the method for forming the catalyst layer include plating,alloy plating, dispersion/composite plating, CVD, PVC, pyrolysis, andspraying. These methods may be used in combination. The catalyst layermay have a plurality of layers and a plurality of elements, as required.The cathode 21 may be subjected to a reduction treatment, as required.As the substrate of the cathode 21, nickel, nickel alloys, andnickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals such as Ru, C,Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd,Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd,Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides andhydroxides of the metals. Examples of the method for forming thecatalyst layer include plating, alloy plating, dispersion/compositeplating, CVD, PVD, pyrolysis, and spraying. These methods may be used incombination. The catalyst layer may have a plurality of layers and aplurality of elements, as required. Nickel, nickel alloys, andnickel-plated iron or stainless, having no catalyst coating may be used.As the substrate of the cathode feed conductor 21, nickel, nickelalloys, and nickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as a material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electro electrolytic cells 1 connected in series. Loweringof the voltage enables the power consumption to be reduced. With themetal elastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis in the present embodiment is paced in the electrolyticcell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantially perpendicular to thepartition wall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane 2 (See FIG. 104). These gaskets can impart airtightness toconnecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced as and be usable for long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 104), each electrolytic cell 1 onto which thegasket is attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

[Laminate]

The electrode for electrolysis in the present embodiment is used as alaminate of a membrane such as an ion exchange membrane or a macroporousmembrane. That is, the laminate in the present embodiment comprises theelectrode for electrolysis and a new membrane. The new membrane is notparticularly limited as long as being separate from the membrane in theexisting electrolyzer, and various known “membranes” can be used. Thematerial, form, physical properties, and the like of the new membranemay be similar to those of the membrane in the existing electrolyzer.Specific examples of the electrode for electrolysis and the membranewill be detailed below.

(Step (A))

In the step of the present embodiment, the electrode for electrolysisand a new membrane are integrated at a temperature at which the membranedoes not melt to thereby obtain a laminate.

The “temperature at which the membrane does not melt” can be identifiedas the softening point of the new membrane. The temperature may varydepending on the material constituting the membrane but is preferably 0to 100° C., more preferably 5 to 80° C., further preferably 10 to 50° C.

The integration described above is preferably performed under normalpressure.

As a specific method for the above integration, which are notparticularly limited, all kinds of methods, except for typical methodsfor melting the membrane such as thermal compression can be used. Onepreferable example is a method in which a liquid is interposed betweenan electrode for electrolysis mentioned below and the membrane and thesurface tension of the liquid is used to integrate the electrode and the“membrane.

[Step (B)]

In the step (B) in the present embodiment, the membrane in the existingelectrolyzer is replaced by a laminate after the step (A). The replacingmethod is not particularly limited, and examples thereof include amethod in which, first in the existing electrolyzer, a fixed state ofthe adjacent electrolytic cell and ion exchange membrane by means of apress device is released to provide a gap between the electrolytic celland the ion exchange membrane, then, the existing ion exchange membraneto be renewed is removed, then, a laminate is inserted into the gap, andthe members are coupled again by means of the press device. By means ofthe method, a laminate can be arranged on the surface of the anode orthe cathode of the existing electrolyzer, and the characteristics of theion exchange membrane and the anode and/or cathode can be renewed.

[Electrode for Electrolysis]

In the present embodiment, the electrode for electrolysis is notparticularly limited as long as the electrode can be integrated with anew membrane as mentioned above, that is, is integratable. The electrodefor electrolysis may be an electrode that serves as the cathode in theelectrolyzer or may be an electrode that serves as an anode. As thematerial, form, and the like of the electrode for electrolysis, thosesuitable may be appropriately selected, in consideration of the steps(A) and (B) in the present embodiment, the configuration of theelectrolyzer, and the like. Hereinbelow, preferable aspects of theelectrode for electrolysis in the present embodiment will be described,but these are merely exemplary aspects preferable for integration with anew membrane. Electrodes for electrolysis other than the aspectsmentioned below can be appropriately employed.

The electrode for electrolysis in the present embodiment has a forceapplied per unit mass·unit area of preferably 1.6 N/(mg·cm²) or less,more preferably less than 1.6 N/(mg·cm²), further preferably less than1.5 N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less from the viewpoint of enabling a goodhandling property to be provided and having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, afeed conductor (a degraded electrode and an electrode having no catalystcoating), and the like. The force applied is even still more preferably1.1 N/mg·cm² or less, further still more preferably 1.10 N/mg·cm² orless, particularly preferably 1.0 N/mg·cm² or less, especiallypreferably 1.00 N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0.2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit is preferably 48 mg/cm² or less, more preferably 30mg/cm² or less, further preferably 20 mg/cm² or less from the viewpointof enabling a good handling property to be provided, having a goodadhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and of economy, and furthermore preferably 15 mg/cm²or less from the comprehensive viewpoint including handling property,adhesion, and economy. The lower limit value is not particularly limitedbut is of the order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as detailed in Examples. As for the force applied, thevalue obtained by the measurement of the method (i) (also referred to as“the force applied (1)”) and the value obtained by the measurement ofthe method (ii) (also referred to as “the force applied (2)”) may thesame or different, and either of the values preferably less than 1.5N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode (130 mm square) are laminated in this order.After this laminate is sufficiently immersed in pure water, excess waterdeposited on the surface of the laminate is removed to obtain a samplefor measurement. The arithmetic average surface roughness (Ra) of thenickel plate after the blast treatment is 0.5 to 0.8 μm. The specificmethod for calculating the arithmetic average surface roughness (Ra) isas described in Examples.

Under conditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method (i)is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. The force ispreferably more than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and furthermore, isfurther more preferably 0.14 N/(mg·cm²), still more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 m.).

[Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurement. Under conditionsof a temperature of 23±2° C. and a relative humidity of 30±5%, only thesample of electrode in this sample for measurement is raised in avertical direction at 10 mm/minute using a tensile and compressiontesting machine, and the load when the sample of electrode is raised by10 mm in a vertical direction is measured. This measurement is repeatedthree times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. Further, the forceis preferably more than 0.005 N/(mg·cm²), more preferably 0.02N/(mg·cm²) or more, further preferably 0.1 N/(mg·cm²) or more from theviewpoint of further improving the electrolytic performance, and isfurther more preferably 0.14 N/(mg·cm²) or more from the viewpoint offurther facilitating handling in a large size (e.g., a size of 1.5 m×2.5m).

The electrode for electrolysis in the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 120 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, being capable of being suitably rolled in aroll and satisfactorily folded, and facilitating handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 μm, more preferably 15 μm.

In the present embodiment, in order to integrate a new membrane and theelectrode for electrolysis, a liquid is preferably interposedtherebetween. As the liquid, any liquid, such as water and organicsolvents, can be used as long as the liquid generates a surface tension.The larger the surface tension of the liquid, the larger the forceapplied between the new membrane and the electrode for electrolysis.Thus, a liquid having a larger surface tension is preferred. Examples ofthe liquid include the following (the numerical value in the parenthesesis the surface tension of the liquid at 20° C.):

hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00 mN/m),ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and water (72.76mN/m).

A liquid having a large surface tension allows the new membrane and theelectrode for electrolysis to be integrated (to be a laminate), andrenewing of the electrode tends to be easier. The liquid between the newmembrane and the electrode for electrolysis may be present in an amountsuch that the both adhere to each other by the surface tension. As aresult, after the laminate is placed in an electrolytic cell, theliquid, if mixed into the electrolyte solution, does not affectelectrolysis itself due to the small amount of the liquid.

From a practical viewpoint, a liquid having a surface tension of 24 mN/mto 80 mN/m, such as ethanol, ethylene glycol, and water, is preferablyused as the liquid. Particularly preferred is water or an alkalineaqueous solution prepared h dissolving caustic soda, potassiumhydroxide, lithium hydroxide, sodium hydrogen carbonate, potassiumhydrogen carbonate, sodium carbonate, potassium carbonate, or the likein water. Alternatively, the surface tension can be adjusted by allowingthese liquids to contain a surfactant. When a surfactant is contained,the adhesion between the new membrane and the electrode for electrolysisvaries to enable the handling property to be adjusted. The surfactant isnot particularly limited, and both ionic surfactants and nonionicsurfactants may be used.

The proportion measured by the following method (2) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda macroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint of further facilitatinghandling in a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from theviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The electrode for electrolysis in the present embodiment preferably has,but is not particularly limited to, a porous structure and an openingratio or void ratio of 5 to 90% or less, from the viewpoint of enablinga good handling property to be provided, having a good adhesive force toa membrane such as an ion exchange membrane and a microporous membrane,a degraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, and preventing accumulation of gas to begenerated during electrolysis. The opening ratio is more preferably 10to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V is calculated fromthe values of the gauge thickness, width, and length of electrode, andfurther, a weight W is measured to thereby enable an opening ratio A tobe calculated by the following formula.

A=(1−(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio can be appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern of a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

Hereinbelow, a more specific embodiment of the electrode forelectrolysis in the present embodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 108, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also as shown FIG. 108, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 108, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol or the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can he used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 μm, more preferably 0.1to 8 μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The curabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness is more preferably 0.1 to 10 μm. The thickness isfurther preferably 0.2 to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thickness ispreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis is measured in the same manner as thethickness of the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

In the present embodiment, the electrode for electrolysis preferablycontains at least one catalytic component selected from the groupconsisting of Ru, Rh, Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn,Y, Zr, Nb, Mo, Ag, Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O,Si, P, S, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, and Dy from the viewpointof achieving sufficient electrolytic performance.

In the present embodiment, from the viewpoint that the electrode forelectrolysis, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a macroporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness or 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking or a coating film under an oxygen atmosphere (pyrolysis), or ionplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst layer is formedon the substrate for electrode for electrolysis by an application stepof applying a coating liquid containing a catalyst, a drying step ofdrying the coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysis isperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable 5 to 20minutes more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 obtained by applying a solution in which metal saltsof various combination are dissolved (first coating liquid) onto thesubstrate for electrode for electrolysis and then pyrolyzing (baking)the coating liquid in the presence of oxygen. The content of the metalin the first coating liquid is substantially equivalent to that in thefirst layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and the further post-bakedfor a long period as required can further improve the stability of thefirst layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating. An exampleincludes a method in which the substrate is fixed in a chamber and themetal ruthenium target is irradiated with an electron beam. Evaporatedmetal ruthenium particles are positively charged in plasma in thechamber to deposit on the substrate negatively charged. The plasmaatmosphere is argon and oxygen, and ruthenium deposits as rutheniumoxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing nickel andtin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal Spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

Hereinafter, an ion exchange membrane according to one aspect of themembrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane is not particularly limited as long as themembrane can be laminated with the electrode for electrolysis, andvarious ion exchange membranes may be employed. In the presentembodiment, an ion exchange membrane that has a membrane body containinga hydrocarbon polymer or fluorine-containing polymer having an ionexchange group and a coating layer provided on at least one surface ofthe membrane body is preferably used. It is preferable that the coatinglayer contain inorganic material particles and a binder and the specificsurface area of the coating layer be 0.1 to 10 m²/g. The ion exchangemembrane having such a structure has a small influence of gas generatedduring electrolysis on electrolytic performance and tends to exertstable electrolytic performance.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO₃—, hereinbelow also referred to as a “sulfonicacid group”) or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂—, hereinbelowalso referred to as a “carboxylic acid group”). From the viewpoint ofstrength and dimension stability, reinforcement core materials arepreferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 109 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containingpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group (a group represented by—CO₂—, hereinbelow also referred to as a “carboxylic acid group”), andthe reinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane 1, as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, is suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 109.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound ispreferably a perfluoro monomer, and a perfluoro monomer selected fromthe group consisting of tetrafluoroethylene, hexafluoropropylene, andperfluoro alkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)₂—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time of hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0.5 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer 2 is located on the cathodeside of the electrolyzer.

The sulfonic acid layer 3 preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂)₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane preferably has a coating layer on at least onesurface of the membrane body. As shown in FIG. 109, in the ion exchangemembrane 1, coating layers 11 a and 11 b are formed on both the surfacesof the membrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably 0.90 to 1.2μm.

Here, the average particle size can be measured by a particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides of Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durabilty, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurites suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contraction of the ion exchange membrane can be controlledin the desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material of the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area of a surface through which substances such asions (an electrolyte solution and cations contained therein (e.g.,sodium ions)) can pass (B) to the area of either one surface of themembrane body (A) (B/A). The total area of the surface through whichsubstances such as ions can pass (B) can refer to the total areas ofregions in which in the ion exchange membrane, cations, an electrolyticsolution, and the like are not blocked by the reinforcement corematerials and the like contained in the ion exchange membrane.

FIG. 110 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 110, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperture ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below. The shape, diameter, or the like of the continuousholes can be controlled by selecting the shape or diameter of thesacrifice core materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapeof sacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step(4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2); Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained by weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based, on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamides and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand, comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include(i) a method in which a fluorine-containing polymer having a carboxylicacid group precursor (e.g., carboxylate functional group) (hereinafter,a layer comprising the same is referred to as the first layer) locatedon the cathode side and a fluorine-containing polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property capable of sufficiently retaining themechanical strength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that is, projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 111(a) and (b) are schematicviews for explaining a method for forming the continuous holes of theion exchange membrane.

FIGS. 111(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 111(a) exemplifies the plain-woven reinforcing material in whichthe reinforcement yarns 52 and sacrifice yarns 504 a are interwovenalong both the longitudinal direction and the lateral direction in thepaper, and the arrangement of the reinforcement yarns 52 and thesacrifice yarns 504 a in the reinforcing material may be varied asrequired.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counterion of the ion exchange group by H+ (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer is more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example andpreferably 30 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactured by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa (also referred to as a Zirfonmembrane in the present embodiment) and those described in InternationalPublication No. WO 2013-183584 and International Publication No. WO2016-203701.

In the present embodiment, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having an EW(ion exchange capacity) different from that of the first ion exchangeresin layer. Additionally, the membrane preferably comprises a first ionexchange resin layer and a second ion exchange resin layer having afunctional group different from that of the first ion exchange resinlayer. The ion exchange capacity can be adjusted by the functional groupto be introduced, and functional groups that may be introduced are asmentioned above.

(Water Electrolysis)

The electrolyzer in the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

Seventh Embodiment

Here, a seventh embodiment of the present invention will be described indetail with reference to FIGS. 112 to 122.

[Method for Producing Electrolyzer]

The method for producing an electrolyzer according to the first aspect(hereinafter, simply referred to as the “first aspect”) of the seventhembodiment (hereinafter, in the section of <Seventh embodiment>, simplyreferred to as “the present embodiment”) is a method for producing a newelectrolyzer arranging a laminate comprising an electrode forelectrolysis and a new membrane in an existing electrolyzer comprisingan anode, a cathode that opposed to the anode, a membrane that is fixedbetween the anode and the cathode, and an electrolyzer frame thatsupports the anode, the cathode, and the membrane, the method comprisinga step (A) of releasing a fixing of the membrane in the electrolyzerframe, and a step (B) of replacing the membrane by the laminate afterthe step (A).

As described above, according to the method for producing anelectrolyzer according to the first aspect, it is possible to renew theelectrode without removing each component to the outside of theelectrolyzer frame, and it is possible to improve the work efficiencyduring electrode renewing in an electrolyzer.

A method for producing an electrolyzer according to a second aspect(hereinbelow, also simply referred to as the “second aspect”) of thepresent embodiment is a method for producing a new electrolyzer byarranging an electrode for electrolysis in an existing electrolyzercomprising an anode, a cathode that is opposed to the anode, a membranethat is fixed between the anode and the cathode, and an electrolyzerframe that supports the anode, the cathode, and the membrane, the methodcomprising a step (A) of releasing a fixing of the membrane in theelectrolyzer frame, and a step (B′) of arranging the electrode forelectrolysis between the membrane and the anode or the cathode after thestep (A).

As described above, also in accordance with the method for producing anelectrolyzer according to the second aspect, it is possible to renew theelectrode without removing each component to the outside of theelectrolyzer frame, and it is possible to improve the work efficiencyduring electrode renewing in an electrolyzer.

Hereinbelow, when referred to as the “method for producing anelectrolyzer according to the present embodiment”, the method forproducing an electrolyzer according to the first aspect and the methodfor producing an electrolyzer according to the second aspect areincorporated.

In the method for producing an electrolyzer according to the presentembodiment, the existing electrolyzer comprises an anode, a cathode thatis opposed to the anode, a membrane that is arranged between the anodeand the cathode, and an electrolyzer frame that supports the anode, thecathode, and the membrane as constituent members. In other words, theexisting electrolyzer comprises a membrane, an electrolytic cell, and anelectrolyzer frame that supports the membrane and the electrolytic cell.The existing electrolyzer is not particularly limited as long ascomprising the constituent members described above, and various knownconfigurations may be employed.

In the method for producing an electrolyzer according to the presentembodiment, a new electrolyzer further comprises an electrode forelectrolysis or a laminate, in addition to a member that has alreadyserved as the anode or cathode in the existing electrolyzer. That is, inthe first aspect and the second aspect, the “electrode for electrolysis”arranged on production of a new electrolyzer serves as the anode orcathode and is separate from the cathode and anode in the existingelectrolyzer. In the method for producing an electrolyzer according tothe present embodiment, even in the case where the electrolyticperformance of the anode and/or cathode has deteriorated in associationwith operation of the existing electrolyzer, arrangement of an electrodefor electrolysis separate therefrom enables the characteristics of theanode and/or cathode to be renewed. In the first aspect, in which alaminate is used, a new ion exchange membrane is arranged incombination, and thus, the characteristics of the ion exchange membranehaving characteristics deteriorated in association with operation can berenewed simultaneously. “Renewing the characteristics” referred toherein means to have characteristics comparable to the initialcharacteristics possessed by the existing electrolyzer before beingoperated or to have characteristics higher than the initialcharacteristics.

In the method for producing an electrolyzer according to the presentembodiment, the existing electrolyzer is assumed to be an “electrolyzerthat has been already operated”, and the new electrolyzer is assumed tobe an “electrolyzer that has not been yet operated”. That is, once anelectrolyzer produced as a new electrolyzer is operated, theelectrolyzer becomes “the existing electrolyzer in the presentembodiment”. Arrangement of an electrode for electrolysis or a laminatein this existing electrolyzer provides “a new electrolyzer of thepresent embodiment”.

Hereinafter, a case of performing common salt electrolysis by using anion exchange membrane as the membrane is taken as an example, and oneembodiment of the electrolyzer will be described in detail. In thesection of <Seventh embodiment>, unless otherwise specified, “theelectrolyzer in the present embodiment” incorporates both “the existingelectrolyzer in the present embodiment” and “the new electrolyzer in thepresent embodiment”.

[Electrolytic Cell]

First, the electrolytic cell, which can be used as a constituent unit ofthe electrolyzer in the present embodiment, will be described. FIG. 112illustrates a cross-sectional view of an electrolytic cell 1.

The electrolytic cell 1 comprises an anode chamber 10, a cathode chamber20, a partition wall 30 placed between the anode chamber 10 and thecathode chamber 20, an anode 11 placed in the anode chamber 10, and acathode 21 placed in the cathode chamber 20. As required, theelectrolytic cell has a substrate 18 a and a reverse current absorbinglayer 18 b formed on the substrate 18 a and may comprise a reversecurrent absorber 18 placed in the cathode chamber. The anode 11 and thecathode 21 belonging to the electrolytic cell 1 are electricallyconnected to each other. In other words, the electrolytic cell 1comprises the following cathode structure. The cathode structure 40comprises the cathode chamber 20, the cathode 21 placed in the cathodechamber 20, and the reverse current absorber 18 placed in the cathodechamber 20, the reverse current absorber 18 has the substrate 18 a andthe reverse current absorbing layer 18 b formed on the substrate 18 a,as shown in FIG. 116, and the cathode 21 and the reverse currentabsorbing layer 18 b are electrically connected. The cathode chamber 20further has a collector 23, a support 24 supporting the collector, and ametal elastic body 22. The metal elastic body 22 is placed between thecollector 23 and the cathode 21. The support 24 is placed between thecollector 23 and the partition wall 30. The collector 23 is electricallyconnected to the cathode 21 via the metal elastic body 22. The partitionwall 30 is electrically connected to the collector 23 via the support24. Accordingly, the partition wall 30, the support 24, the collector23, the metal elastic body 22, and the cathode 21 are electricallyconnected. The cathode 21 and the reverse current absorbing layer 18 bare electrically connected. The cathode 21 and the reverse currentabsorbing layer ma be directly connected or may be indirectly connectedvia the collector, the support, the metal elastic body, the partitionwall, or the like. The entire surface of the cathode 21 is preferablycovered with a catalyst layer for reduction reaction. The form ofelectrical connection may be a form in which the partition wall 30 andthe support the support 24 and the collector 23, and the collector 23and the metal elastic body 22 are each directly attached and the cathode21 is laminated on the metal elastic body 22. Examples of a method fordirectly attaching these constituent members to one another includewelding and the like. Alternatively, the reverse current absorber 18,the cathode 21, and the collector 23 may be collectively referred to asa cathode structure 40.

FIG. 113 illustrates a cross-section view of two electrolytic cells 1that are adjacent in the electrolyzer 4. FIG. 114 shows an electrolyzer4 as an existing electrolyzer. FIG. 115 shows a step of assembling theelectrolyzer (different from steps (A) to (B) and steps (A′) to (B′)).

As shown in FIG. 113, an electrolytic cell 1, a cation exchange membrane2, and an electrolytic cell 1 are arranged in series in the ordermentioned. An ion exchange membrane 2 is arranged between the anodechamber of one electrolytic cell 1 of the two electrolytic cells thatare adjacent in the electrolyzer and the cathode chamber of the otherelectrolytic cell 1. That is, the anode chamber 10 of the electrolyticcell 1 and the cathode chamber 20 of the electrolytic cell 1 adjacentthereto is separated by the cation exchange membrane 2. As shown in FIG.114, the electrolyzer 4 is composed such that the plurality ofelectrolytic cells 1 connected in series via the ion exchange membranes2 are supported by an electrolyzer frame 8. That is, the electrolyzer 4is a bipolar electrolyzer comprising the plurality of electrolytic cells1 arranged in series and ion exchange membranes 2 each arranged betweenadjacent electrolytic cells 1, and the electrolyzer frame 8 thatsupports the cells 1 and the membranes 2. As shown in FIG. 115, theelectrolyzer 4 is assembled by arranging the plurality of electrolyticcells 1 connected in series via the ion exchange membrane 2 and couplingthe cells by means of a press device 5 in the electrolyzer frame 8. Theelectrolyzer frame is not particularly limited as long as being capableof supporting each of the member as well as coupling the members, andvarious known configurations may be employed. The device for couplingeach of the members, possessed by the electrolyzer frame, is notparticularly limited, and examples thereof include hydraulic presses anddevices comprising a tie rod as a mechanism.

The electrolyzer 4 has an anode terminal 7 and a cathode terminal 6 tobe connected to a power supply. The anode 11 of the electrolytic cell 1located at farthest end among the plurality of electrolytic cells 1coupled in series in the electrolyzer 4 is electrically connected to theanode terminal 7. The cathode 21 of the electrolytic cell located at theend opposite to the anode terminal 7 among the plurality of electrolyticcells 1 coupled in series in the electrolyzer 4 is electricallyconnected to the cathode terminal 6. The electric current duringelectrolysis flows from the side of the anode terminal 7, through theanode and cathode of each electrolytic cell 1, toward the cathodeterminal 6. At the both ends of the coupled electrolytic cells 1, anelectrolytic cell having an anode chamber only (anode terminal cell) andan electrolytic cell having a cathode chamber only (cathode terminalcell) may be arranged. In this case, the anode terminal 7 is connectedto the anode terminal cell arranged at the one end, and the cathodeterminal 6 is connected to the cathode terminal cell arranged at theother end.

In the case of electrolyzing brine, brine is supplied to each anodechamber 10, and pure water or a low-concentration sodium hydroxideaqueous solution is supplied to each cathode chamber 20. Each liquid issupplied from an electrolyte solution supply pipe (not shown in Figure),through an electrolyte solution supply hose (not shown in Figure), toeach electrolytic cell 1. The electrolyte solution and products fromelectrolysis are recovered from an electrolyte solution recovery pipe(not shown in Figure). During electrolysis, sodium ions in the brinemigrate from the anode chamber 10 of the one electrolytic cell 1,through the ion exchange membrane 2, to the cathode chamber 20 of theadjacent electrolytic cell 1. Thus, the electric current duringelectrolysis flows in the direction in which the electrolytic cells 1are coupled in series. That is, the electric current flows, through thecation exchange membrane 2, from the anode chamber 10 toward the cathodechamber 20. As the brine is electrolyzed, chlorine gas is generated onthe side of the anode 11, and sodium hydroxide (solute) and hydrogen gasare generated on the side of the cathode 21.

(Anode Chamber)

The anode chamber 10 has the anode 11 or anode feed conductor 11. Thefeed conductor herein referred to mean a degraded electrode (i.e., theexisting electrode), an electrode having no catalyst coating, and thelike. When the electrode for electrolysis in the present embodiment isinserted to the anode side, 11 serves as an anode feed conductor. Whenthe electrode for electrolysis in the present embodiment is not insertedto the anode side, 11 serves as an anode. The anode chamber 10preferably has an anode-side electrolyte solution supply unit thatsupplies an electrolyte solution to the anode chamber 10, a baffle platethat is arranged above the anode-side electrolyte solution supply unitso as to be substantially parallel or oblique to a partition wall 30,and an anode-side gas liquid separation unit that is arranged above thebaffle plate to separate gas from the electrolyte solution including thegas mixed.

(Anode)

When the electrode for electrolysis in the present embodiment is notinserted to the anode side, an anode 11 is provided in the frame of theanode chamber 10 (i.e., the anode frame). As the anode 11, a metalelectrode such as so-called DSA(R) can be used. DSA is an electrodeincluding a titanium substrate of which surface is covered with an oxidecomprising ruthenium, iridium, and titanium as components.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the anode side, the anode feed conductor 11 is provided inthe frame of the anode chamber 10. As the anode feed conductor 11, ametal electrode such as so-called DSA(R) can be used, and titaniumhaving no catalyst coating can be also used. Alternatively, DSA having athinner catalyst coating can be also used. Further, a used anode can bealso used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Anode-Side Electrolyte Solution Supply Unit)

The anode-side electrolyte solution supply unit, which supplies theelectrolyte solution to the anode chamber 10, is connected to theelectrolyte solution supply pipe. The anode-side electrolyte solutionsupply unit is preferably arranged below the anode chamber 10. As theanode-side electrolyte solution supply unit, for example, a pipe on thesurface of which aperture portions are formed (dispersion pipe) and thelike can be used. Such a pipe is more preferably arranged along thesurface of the anode 11 and parallel to the bottom 19 of theelectrolytic cell. This pipe is connected to an electrolyte solutionsupply pipe (liquid supply nozzle) that supplies the electrolytesolution into the electrolytic cell 1. The electrolyte solution suppliedfrom the liquid supply nozzle is conveyed with a pipe into theelectrolytic cell 1 and supplied from the aperture portions provided onthe surface of the pipe to inside the anode chamber 10. Arranging thepipe along the surface of the anode 11 and parallel to the bottom 19 ofthe electrolytic cell is preferable because the electrolyte solution canbe uniformly supplied to inside the anode chamber 10.

(Anode-Side Gas Separation Unit)

The anode-side gas liquid separation unit is preferably arranged abovethe baffle plate. The anode-side gas liquid separation unit has afunction of separating produced gas such as chlorine gas from theelectrolyte solution during electrolysis. Unless otherwise specified,above means the upper direction in the electrolytic cell 1 in FIG. 112,and below means the lower direction in the electrolytic cell 1 in FIG.112.

During electrolysis, produced gas generated in the electrolytic cell 1and the electrolyte solution form a mixed phase (gas-liquid mixedphase), which is then emitted out of the system. Subsequently, pressurefluctuations inside the electrolytic cell 1 cause vibration, which mayresult in physical damage of the ion exchange membrane. In order toprevent this event, the electrolytic cell 1 in the present embodiment ispreferably provided with an anode-side gas liquid separation unit toseparate the gas from the liquid. The anode-side gas liquid separationunit is preferably provided with a defoaming plate to eliminate bubbles.When the gas-liquid mixed phase flow passes through the defoaming plate,bubbles burst to thereby enable the electrolyte solution and the gas tobe separated. As a result, vibration during electrolysis can beprevented.

(Baffle Plate)

The baffle plate is preferably arranged above the anode-side electrolytesolution supply unit and arranged substantially in parallel with orobliquely to the partition wall 30. The baffle plate is a partitionplate that controls the flow of the electrolyte solution in the anodechamber 10. When the baffle plate is provided, it is possible to causethe electrolyte solution (brine or the like) to circulate internally inthe anode chamber 10 to thereby make the concentration uniform. In orderto cause internal circulation, the baffle plate is preferably arrangedso as to separate the space in proximity to the anode 11 from the spacein proximity to the partition wall 30. From such a viewpoint, the baffleplate is preferably placed so as to be opposed to the surface of theanode 11 and to the surface of the partition wall 30. In the space inproximity to the anode partitioned by the baffle plate, as electrolysisproceeds, the electrolyte solution concentration (brine concentration)is lowered, and produced gas such as chlorine gas is generated. Thisresults in a difference in the gas-liquid specific gravity between thespace in proximity to anode 11 and the space in proximity to thepartition wall 30 partitioned by the baffle plate. By use of thedifference, it is possible to promote the internal circulation of theelectrolyte solution in the anode chamber 10 to thereby make theconcentration distribution of the electrolyte solution in the anodechamber 10 more uniform.

Although not shown in FIG. 112, a collector may be additionally providedinside the anode chamber 10. The material and configuration of such acollector may be the same as those of the collector of the cathodechamber mentioned below. In the anode chamber 10, the anode 11 per semay also serve as the collector.

(Partition Wall)

The partition wall 30 is arranged between the anode chamber 10 and thecathode chamber 20. The partition wall 30 may be referred to as aseparator, and the anode chamber 10 and the cathode chamber 20 arepartitioned by the partition wall 30. As the partition wall 30, oneknown as a separator for electrolysis can be used, and an examplethereof includes a partition wall formed by welding a plate comprisingnickel to the cathode side and a plate comprising titanium to the anodeside.

(Cathode Chamber)

In the cathode chamber 20, when the electrode for electrolysis in thepresent embodiment is inserted to the cathode side, 21 serves as acathode feed conductor. When the electrode for electrolysis in thepresent embodiment is not inserted to the cathode side, 21 serves as acathode. When a reverse current absorber is included, the cathode orcathode feed conductor 21 is electrically connected to the reversecurrent absorber. The cathode chamber 20, similarly to the anode chamber10, preferably has a cathode-side electrolyte solution supply unit and acathode-side gas liquid separation unit. Among the componentsconstituting the cathode chamber 20, components similar to thoseconstituting the anode chamber 10 be not described.

(Cathode)

When the electrode for electrolysis in the present embodiment is notinserted to the cathode side, a cathode 21 is provided in the frame ofthe cathode chamber 20 (i.e., cathode frame). The cathode 21 preferablyhas a nickel substrate and a catalyst layer that covers the nickelsubstrate. Examples of the components of the catalyst layer on thenickel substrate include metals such as Ru, C, Si, P, S, Al, Ti, V, Cr,Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag, Cd, In, Sn, Ta, W,Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy,Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides of the metals.Examples of the method for forming the catalyst layer include plating,alloy plating, dispersion/composite plating, CVD, PVD, pyrolysis, andspraying. These methods may be used in combination. The catalyst layermay have a plurality of layers and a plurality of elements, as required.The cathode 21 may be subjected to a reduction treatment, as required.As the substrate of the cathode 21, nickel, nickel alloys, andnickel-plated iron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Cathode Feed Conductor)

When the electrode for electrolysis in the present embodiment isinserted to the cathode side, a cathode feed conductor 21 is provided inthe frame of the cathode chamber 20. The cathode feed conductor 21 maybe covered with a catalytic component. The catalytic component may be acomponent that is originally used as the cathode and remains. Examplesof the components of the catalyst layer include metals su as Ru, C, Si,P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Rh, Pd, Ag,Cd, In, Sn, Ta, W, Re, Os, Ir, Pt, Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm,Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu, and oxides and hydroxides ofthe metals. Examples of the method for forming the catalyst layerinclude plating, alloy plating, dispersion/composite plating, CVD, PVD,pyrolysis, and spraying. These methods may be used in combination. Thecatalyst layer may have a plurality of layers and a plurality ofelements, as required. Nickel, nickel alloys, and nickel-plated iron orstainless, having no catalyst coating may be used. As the substrate ofthe cathode feed conductor 21, nickel, nickel alloys, and nickel-platediron or stainless may be used.

As the form, any of a perforated metal, nonwoven fabric, foamed metal,expanded metal, metal porous foil formed by electroforming, so-calledwoven mesh produced by knitting metal lines, and the like can be used.

(Reverse Current Absorbing Layer)

A material having a redox potential less noble than the redox potentialof the element for the catalyst layer of the cathode mentioned above maybe selected as material for the reverse current absorbing layer.Examples thereof include nickel and iron.

(Collector)

The cathode chamber 20 preferably comprises the collector 23. Thecollector 23 improves current collection efficiency. In the presentembodiment, the collector 23 is a porous plate and is preferablyarranged in substantially parallel to the surface of the cathode 21.

The collector 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The collector 23 maybe a mixture, alloy, or composite oxide of these metals. The collector23 may have any form as long as the form enables the function of thecollector and may have a plate or net form.

(Metal Elastic Body)

Placing the metal elastic body 22 between the collector 23 and thecathode 21 presses each cathode 21 of the plurality of electrolyticcells 1 connected in series onto the ion exchange membrane 2 to reducethe distance between each anode 11 and each cathode 21. Then, it ispossible to lower the voltage to be applied entirely across theplurality of electrolytic cells 1 connected in series. Lowering of thevoltage enables the power consumption to be reduced. With the metalelastic body 22 placed, the pressing pressure caused by the metalelastic body 22 enables the electrode for electrolysis to be stablymaintained in place when the laminate including the electrode forelectrolysis in the present embodiment placed in the electroelectrolytic cell.

As the metal elastic body 22, spring members such as spiral springs andcoils and cushioning mats may be used. As the metal elastic body 22, asuitable one may be appropriately employed, in consideration of a stressto press the ion exchange membrane and the like. The metal elastic body22 may be provided on the surface of the collector 23 on the side of thecathode chamber 20 or may be provided on the surface of the partitionwall on the side of the anode chamber 10. Both the chambers are usuallypartitioned such that the cathode chamber 20 becomes smaller than theanode chamber 10. Thus, from the viewpoint of the strength of the frameand the like, the metal elastic body 22 is preferably provided betweenthe collector 23 and the cathode 21 in the cathode chamber 20. The metalelastic body 23 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium.

(Support)

The cathode chamber 20 preferably comprises the support 24 thatelectrically connects the collector 23 to the partition wall 30. Thiscan achieve an efficient current flow.

The support 24 preferably comprises an electrically conductive metalsuch as nickel, iron, copper, silver, and titanium. The support 24 mayhave any shape as long as the support can support the collector 23 andmay have a rod, plate, or net shape. The support 24 has a plate shape,for example. A plurality of supports 24 are arranged between thepartition wall 30 and the collector 23. The plurality of supports 24 arealigned such that the surfaces thereof are in parallel to each other.The supports 24 are arranged substantially perpendicular to thepartition wall 30 and the collector 23.

(Anode Side Gasket and Cathode Side Gasket)

The anode side gasket is preferably arranged on the frame surfaceconstituting the anode chamber 10. The cathode side gasket is preferablyarranged on the frame surface constituting the cathode chamber 20.Electrolytic cells are connected to each other such that the anode sidegasket included in one electrolytic cell and the cathode side gasket ofan electrolytic cell adjacent to the cell sandwich the ion exchangemembrane 2 (see FIG. 113). These gaskets can impart airtightness toconnecting points when the plurality of electrolytic cells 1 isconnected in series via the ion exchange membrane 2.

The gaskets form a seal between the ion exchange membrane andelectrolytic cells. Specific examples of the gaskets include pictureframe-like rubber sheets at the center of which an aperture portion isformed. The gaskets are required to have resistance against corrosiveelectrolyte solutions or produced gas and be usable for a long period.Thus, in respect of chemical resistance and hardness, vulcanizedproducts and peroxide-crosslinked products of ethylene-propylene-dienerubber (EPDM rubber) and ethylene-propylene rubber (EPM rubber) areusually used as the gaskets. Alternatively, gaskets of which region tobe in contact with liquid (liquid contact portion) is covered with afluorine-containing resin such as polytetrafluoroethylene (PTFE) andtetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA) may beemployed as required. These gaskets each may have an aperture portion soas not to inhibit the flow of the electrolyte solution, and the shape ofthe aperture portion is not particularly limited. For example, a pictureframe-like gasket is attached with an adhesive or the like along theperipheral edge of each aperture portion of the anode chamber frameconstituting the anode chamber 10 or the cathode chamber frameconstituting the cathode chamber 20. Then, for example, in the casewhere the two electrolytic cells 1 are connected via the ion exchangemembrane 2 (see FIG. 113), each electrolytic cell 1 onto which thegasket is attached should be tightened via ion exchange membrane 2. Thistightening can prevent the electrolyte solution, alkali metal hydroxide,chlorine gas, hydrogen gas, and the like generated from electrolysisfrom leaking out of the electrolytic cells 1.

[Laminate]

In the method for producing an electrolyzer according to the presentembodiment, the electrode for electrolysis can be used as a laminate ofa membrane such as an ion exchange membrane or a microporous membrane.That is, the laminate in the present embodiment comprises the electrodefor electrolysis and a new membrane. The new membrane is notparticularly limited as long as being separate from the membrane in theexisting electrolyzer, and various known “membranes” can be used. Thematerial, form, physical properties, and the like of the new membranemay be similar to those of the membrane in the existing electrolyzer.Specific examples of the electrode for electrolysis and the membranewill be detailed below.

(Step (A))

In the step (A) in the first aspect, fixing of the membrane is releasedin the electrolyzer frame. “In the electrolyzer frame” means that thestep (A) is performed while a state is maintained in which theelectrolytic cell (that is, the member comprising the anode and thecathode) and the membrane are supported by the electrolyzer frame, andan aspect in which the electrolytic cell is removed from theelectrolyzer frame is excluded. Examples of a method for releasing afixing of the membrane include, but not particularly limited to, amethod in which pressing by a press device in the electrolyzer frame isreleased to form a gap between the electrolytic cell and the membrane soas to enable the membrane to be removable to the outside of theelectrolyzer frame. In the step (A), fixing of the membrane ispreferably released in the electrolyzer frame by sliding the anode andthe cathode in the arrangement direction thereof, respectively. Theoperation enables the membrane to be removable to the outside of theelectrolyzer frame without removing the electrolytic cell to the outsideof the electrolyzer frame.

[Step (B)]

In the step (B) in the first aspect, the membrane in the existingelectrolyzer is replaced by a laminate after the step (A). Examples ofthe replacing method include, but not particularly limited to, a methodin which a gap is formed between the electrolytic cell and the ionexchange membrane, then, the existing membrane to be renewed is removed,and then, a laminate is inserted into the gap. By means of the method, alaminate can be arranged on the surface of the anode or the cathode ofthe existing electrolyzer, and the characteristics of the ion exchangemembrane and the anode and/or cathode can be renewed.

After the step (B) is performed, the laminate is preferably fixed in theelectrolyzer frame by pressing from the anode and the cathode.Specifically, after the membrane is replaced by the laminate theexisting electrolyzer, the laminate and the members in the existingelectrolyzer such as the electrolytic cell can be coupled by pressingagain by means of the press device. By means of the method, a laminatecan be fixed on the surface of the anode or the cathode in the existingelectrolyzer.

A specific example of the steps (A) to (B) in the first aspect will bedescribed based on FIGS. 117(A) and (B). First, pressing by a pressdevice 5 is released, and a plurality of electrolytic cells 1 and ionexchange membranes 2 are slid in the arrangement direction thereof α.This enables a gap S to be formed between the electrolytic cell 1 andthe ion exchange membrane 2 without removing the electrolytic cell 1 tothe outside of the electrolyzer frame 8, and the ion exchange membrane 2become removable to the outside of the electrolyzer frame 8.Subsequently, the ion exchange membrane 2 to be replaced of the existingelectrolyzer is removed out of the electrolyzer frame 8, and a laminate9 of a new ion exchange membrane 2 a and an electrode for electrolysis100 instead is inserted between adjacent electrolytic cells 1 (that is,the gap S). In this manner, the laminate 9 is arranged between theadjacent electrolytic cells 1, and these components become supported bythe electrolyzer frame 8. Then, the plurality of electrolytic cells 1and the laminate 9 are coupled by being pressed in the arrangementdirection α by means of the press device S.

(Step (A′))

Also in the step (A′) in the second aspect, fixing of the membrane isreleased in the electrolyzer frame, as in the first aspect. Also in thestep (A′), fixing of the membrane is preferably released in theelectrolyzer frame by sliding the anode and the cathode in thearrangement direction thereof, respectively. The operation enables themembrane to be removable to the outside of the electrolyzer framewithout removing the electrolytic cell to the outside of theelectrolyzer frame.

[Step (B′)]

In the step (B′) in the second aspect, an electrode for electrolysis isarranged between the membrane and the anode or cathode after the step(A′). Examples of the method for arranging an electrode for electrolysisinclude, but not particularly limited, a method in which, for example, agap is formed between the electrolytic cell and the ion exchangemembrane, and then, an electrode for electrolysis is inserted into thegap. By means of the method, the electrode for electrolysis can bearranged on the surface of the anode or cathode in the existingelectrolyzer, and the characteristics of the anode or cathode can berenewed.

After the step (B′) is performed, the electrode for electrolysis ispreferably fixed in electrolyzer frame by pressing from the anode andthe cathode. Specifically, after the electrode for electrolysis isarranged on the surface of the anode or cathode in the existingelectrolyzer, the electrode for electrolysis and the members in theexisting electrolyzer such as the electrolytic cell can be coupled bypressing again by means of the press device. By means of the method, alaminate can be fixed on the surface of the anode or the cathode in theexisting electrolyzer.

A specific example of the steps (A′) to (B′) in the second aspect willbe described based on FIGS. 118(A) and (B). First, pressing by a pressdevice 5 is released, and a plurality of electrolytic cells 1 and ionexchange membranes 2 are slid in the arrangement direction thereof α.This enables a gap S to be formed between the electrolytic cell 1 andthe ion exchange membrane 2 without removing the electrolytic cell 1 tothe outside of the electrolyzer frame 8. Then, the electrode forelectrolysis 100 is inserted between the adjacent electrolytic cells 1(that is, into the gap S) In this manner, the electrode for electrolysis100 is arranged between the adjacent electrolytic cells 1, and thesecomponents become supported by the electrolyzer frame 8. Then, theplurality of electrolytic cells 1 and the electrode for electrolysis 100are coupled by being pressed in the arrangement direction a by means ofthe press device 5.

In the step (B) in the first aspect, the laminate is preferably fixed onthe surface of at least one of the anode and cathode at a temperature atwhich the laminate does not melt.

The “temperature at which the laminate does not melt” can be identifiedas the softening point of the new membrane. The temperature may varydepending on the material constituting the membrane but is preferably 0to 100° C., more preferably 5 to 80° C., further preferably 10 to 50° C.

The fixing described above is preferably performed under normalpressure.

Further, the laminate is preferably obtained by integrating theelectrode for electrolysis and the new membrane at a temperature atwhich the membrane does not melt and then used in the step (B).

As a specific method for the above integration, which are notparticularly limited, all kinds of methods, except for typical methodsfor melting the membrane such as thermal compression can be used. Onepreferable example is a method in which a liquid is interposed betweenan electrode for electrolysis mentioned below and the membrane and thesurface tension of the liquid is used to integrate the electrode and themembrane.

[Electrode for Electrolysis]

In the method for producing an electrolyzer according to the presentembodiment, the electrode for electrolysis is not particularly limitedas long as the electrode can be used for electrolysis. The electrode forelectrolysis may be an electrode that serves as the cathode in theelectrolyzer or may be an electrode that serves as an anode. As thematerial, form, and the like of the electrode for electrolysis, thosesuitable may be appropriately selected, in consideration of theconfiguration of the electrolyzes and the like. Hereinbelow, preferableaspects of the electrode for electrolysis in the present embodiment willbe described, but these are merely exemplary preferable aspects for acase in which the electrode is integrated with a new membrane to form alaminate in the first aspect. Electrodes for electrolysis other than theaspects mentioned below can be appropriately employed.

The electrode for electrolysis in the present embodiment has a forceapplied per unit mass·unit area of preferably 1.6 N/(mg·cm²) or less,more preferably less than 1.6 N/(mg·cm²), further preferably less than1.5 N/(mg·cm²), even further preferably 1.2 N/mg·cm² or less, still morepreferably 1.20 N/mg·cm² or less from the viewpoint of enabling a goodhandling property to be provided and having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, afeed conductor (a degraded electrode and an electrode having no catalystcoating), and the like. The force applied is even still more preferably1.1 N/mg·cm² or less, further still more preferably 1.10 N/mg·cm² orless, particularly preferably 1.0 N/mg·cm² or less, especiallypreferably 1.00 N/mg·cm² or less.

From the viewpoint of further improving the electrolytic performance,the force is preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/mg·cm² or more, furthermore preferably 0.14 N/(mg·cm²) or more. The force is further morepreferably 0.2 N/(mg·cm²) or more from the viewpoint of furtherfacilitating handling in a large size (e.g., a size of 1.5 m×2.5 m).

The force applied described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, arithmetic average surface roughness, andthe like, for example. More specifically, for example, a higher openingratio tends to lead to a smaller force applied, and a lower openingratio tends to lead to a larger force applied.

The mass per unit is preferable 48 mg/cm² or less, more preferably 30mg/cm² or less, further preferably 20 mg/cm² or less from the viewpointof enabling a good handling property to be provided, having a goodadhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode, a feed conductor having nocatalyst coating, and of economy, and furthermore is preferably 15mg/cm² or less from the comprehensive viewpoint including handlingproperty, adhesion, and economy. The lower limit value is notparticularly limited but is of the order of 1 mg/cm², for example.

The mass per unit area described above can be within the range describedabove by appropriately adjusting an opening ratio described below,thickness of the electrode, and the like, for example. Morespecifically, for example, when the thickness is constant, a higheropening ratio tends to lead to a smaller mass per unit area, and a loweropening ratio tends to lead to a larger mass per unit area.

The force applied can be measured by methods (i) or (ii) describedbelow, which are as detailed in Examples. As for the force applied, thevalue obtained by the measurement of the method (i) (also referred to as“the force applied (1)”) and the value obtained by the measurement ofthe method (ii) (also referred to as “the force applied (2)”) may be thesame or different, and either of the values is preferably less than 1.5N/mg·cm².

[Method (i)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square), an ion exchange membranewhich is obtained by applying inorganic material particles and a binderto both surfaces of a membrane of a perfluorocarbon polymer into whichan ion exchange group is introduced (170 mm square, the detail of theion exchange membrane referred to herein is as described in Examples),and a sample of electrode (130 mm square) are laminated in this order.After this laminate is sufficiently immersed in pure water, excess waterdeposited on the surface of the laminate is removed to obtain a samplefor measurement. The arithmetic average surface roughness (Ra) of thenickel plate after the blast treatment is 0.5 to 0.8 μm. The specificmethod for calculating the arithmetic average surface roughness (Ra) isas described in Examples.

Under conditions of a temperature of 23+2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the ion exchange membrane and the mass ofthe portion overlapping the ion exchange membrane in the sample ofelectrode to calculate the force applied per unit mass·unit area (1)(N/mg·cm²).

The force applied per unit mass·unit area (1) obtained by the method (i)preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is everstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. The force ispreferably more Than 0.005 N/(mg·cm²), more preferably 0.08 N/(mg·cm²)or more, further preferably 0.1 N/(mg·cm²) or more from the viewpoint offurther improving the electrolytic performance, and furthermore, isfurther more preferably 0.14 N/(mg·cm²), still more preferably 0.2N/(mg·cm²) or more from the viewpoint of further facilitating handlingin a large size (e.g., a size of 1.5 m×2.5 T). [Method (ii)]

A nickel plate obtained by blast processing with alumina of grain-sizenumber 320 (thickness 1.2 mm, 200 mm square, a nickel plate similar tothat of the method (i) above) and a sample of electrode (130 mm square)are laminated in this order. After this laminate is sufficientlyimmersed in pure water, excess water deposited on the surface of thelaminate is removed to obtain a sample for measurements. Underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, only the sample of electrode in this sample for measurement israised in a vertical direction at 10 mm/minute using a tensile andcompression testing machine, and the load when the sample of electrodeis raised by 10 mm in a vertical direction is measured. This measurementis repeated three times, and the average value is calculated.

This average value is divided by the area of the overlapping portion ofthe sample of electrode and the nickel plate and the mass of the sampleof electrode in the portion overlapping the nickel plate to calculatethe adhesive force per unit mass·unit area (2) (N/mg·cm²).

The force applied per unit mass·unit area (2) obtained by the method(ii) is preferably 1.6 N/(mg·cm²) or less, more preferably less than 1.6N/(mg·cm²), further preferably less than 1.5 N/(mg·cm²), even furtherpreferably 1.2 N/mg·cm² or less, still more preferably 1.20 N/mg·cm² orless from the viewpoint of enabling a good handling property to beprovided and having a good adhesive force to a membrane such as an ionexchange membrane and a microporous membrane, a degraded electrode, anda feed conductor having no catalyst coating. The force applied is evenstill more preferably 1.1 N/mg·cm² or less, further still morepreferably 1.10 N/mg·cm² or less, particularly preferably 1.0 N/mg·cm²or less, especially preferably 1.00 N/mg·cm² or less. Further, the forceis preferably more than 0.005 N/(mg·cm²), more preferably 0.08N/(mg·cm²) or more, further preferably 0.1 N/(mg·cm²) or more from theviewpoint of further improving the electrolytic performance, and isfurther more preferably 0.14 N/(mg·cm²) or more from the viewpoint offurther facilitating handling in a large size (e.g., a size of 1.5 m×2.5m).

The electrode for electrolysis in the present embodiment preferablyincludes a substrate for electrode for electrolysis and a catalystlayer. The thickness of the substrate for electrode for electrolysis(gauge thickness) is, but is not particularly limited to, preferably 300μm or less, more preferably 205 μm or less, further preferably 155 μm orless, further more preferably 135 μm or less, even further morepreferably 125 μm or less, still more preferably 120 μm or less, evenstill more preferably 100 μm or less from the viewpoint of enabling agood handling property to be provided, having a good adhesive force to amembrane such as an ion exchange membrane and a microporous membrane, adegraded electrode (feed conductor), and an electrode (feed conductor)having no catalyst coating, being capable of being suitably rolled in aroll and satisfactorily folded, and facilitating handling in a largesize (e.g., a size of 1.5 m×2.5 m), and is further still more preferably50 μm or less from the viewpoint of a handling property and economy. Thelower limit value is not particularly limited, but is 1 μm, for example,preferably 5 μm, more preferably 15 μm.

In the method for producing an electrolyzer according to the presentembodiment, in order to integrate a new membrane and the electrode forelectrolysis, a liquid is preferably interposed therebetween. As theliquid, any liquid, such as water and organic solvents, can be used aslong as the liquid generates a surface tension. The larger the surfacetension of the liquid, the larger the force applied between the newmembrane and the electrode for electrolysis. Thus, a liquid having alarger surface tension is preferred. Examples of the liquid include thefollowing (the numerical value in the parentheses is the surface tensionof the liquid at 20° C.):

hexane (20.44 mN/m), acetone (23.30 mN/m), methanol (24.00 mN/m),ethanol (24.05 mN/m), ethylene glycol (50.21 mN/m), and water (72.76mN/m).

A liquid having a large surface tension allows the new membrane and theelectrode for electrolysis to be integrated (to be a laminate), andrenewing of the electrode tends to be easier. The liquid between the newmembrane and the electrode for electrolysis may be present in an amountsuch that the both adhere to each other by the surface tension. As aresult, after the laminate is placed in an electrolytic cell, theliquid, if mixed into the electrolyte solution, does not affectelectrolysis itself due to the small amount of the liquid.

From a practical viewpoint, a liquid having a surface tension of 24 mN/mto 80 mN/m, such as ethanol, ethylene glycol, and water, is preferablyused as the liquid. Particularly preferred is water or an alkalineaqueous solution prepared by dissolving caustic soda, potassiumhydroxide, lithium hydroxide, sodium hydrogen carbonate, potassiumhydrogen carbonate, sodium carbonate, potassium carbonate, or the likein water. Alternatively, the surface tension can be adjusted by allowingthese liquids to contain a surfactant. When a surfactant is contained,the adhesion be the new membrane and the electrode for electrolysisvaries to enable the handling property to be adjusted. The surfactant isnot particularly limited, and both ionic surfactants and nonionicsurfactants may be used.

The proportion measured by the following method (2) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 90% or more, more preferably 92% or more from theviewpoint of enabling a good handling property to be provided and havinga good adhesive force to a membrane such as an ion exchange membrane anda microporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and furtherpreferably 95% or more from the viewpoint of further facilitatinghandling a large size (e.g., a size of 1.5 m×2.5 m). The upper limitvalue is 100%.

[Method (2)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 280 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The proportion measured by the following method (3) of the electrode forelectrolysis in the present embodiment is not particularly limited, butis preferably 75% or more, more preferably 80% or more from tteviewpoint of enabling a good handling property to be provided, having agood adhesive force to a membrane such as an ion exchange membrane and amicroporous membrane, a degraded electrode (feed conductor), and anelectrode (feed conductor) having no catalyst coating, and being capableof being suitably rolled in a roll and satisfactorily folded, and isfurther preferably 90% or more from the viewpoint of furtherfacilitating handling in a lame size (e.g., a size of 1.5 m×2.5 m). Theupper limit value is 100%.

[Method (3)]

An ion exchange membrane (170 mm square) and a sample of electrode (130mm square) are laminated in this order. The laminate is placed on acurved surface of a polyethylene pipe (outer diameter: 145 mm) such thatthe sample of electrode in this laminate is positioned outside underconditions of a temperature of 23±2° C. and a relative humidity of30±5%, the laminate and the pipe are sufficiently immersed in purewater, excess water deposited on a surface of the laminate and the pipeis removed, and one minute after this removal, then the proportion (%)of an area of a portion in which the ion exchange membrane (170 mmsquare) is in close contact with the sample of electrode is measured.

The electrode for electrolysis in the present embodiment preferably has,but is not particularly limited to, a porous structure and an openingratio or void ratio of 5 to 90% or less, from the viewpoint of enablinga good handling property, to be provided, having a good adhesive forceto a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode (feed conductor), and an electrode (feedconductor) having no catalyst coating, and preventing accumulation ofgas to be generated during electrolysis. The opening ratio is morepreferably 10 to 80% or less, further preferably 20 to 75%.

The opening ratio is a proportion of the opening portions per unitvolume. The calculation method may differ depending on that openingportions in submicron size are considered or that only visible openingsare considered. In the present embodiment, a volume V is calculated fromthe values of the gauge thickness, width, and length of electrode, andfurther, a weight W is measured to thereby enable an opening ratio A tobe calculated by the following formula.

A=(1−(W/(V×ρ))×100

ρ is the density of the electrode material (g/cm³). For example, ρ ofnickel is 8.908 g/cm³, and ρ of titanium is 4.506 g/cm³. The openingratio can be appropriately adjusted by changing the area of metal to beperforated per unit area in the case of perforated metal, changing thevalues of the SW (short diameter), LW (long diameter), and feed in thecase of expanded metal, changing the line diameter of metal fiber andmesh number in the case of mesh, changing the pattern or a photoresistto be used in the case of electroforming, changing the metal fiberdiameter and fiber density in the case of nonwoven fabric, changing themold for forming voids in the case of foamed metal, or the like.

Hereinbelow, a more specific embodiment of the electrode forelectrolysis in the present embodiment will be described.

The electrode for electrolysis according to the present embodimentpreferably includes a substrate for electrode for electrolysis and acatalyst layer. The catalyst layer may be composed of a plurality oflayers as shown below or may be a single-layer configuration.

As shown in FIG. 119, an electrode for electrolysis 100 according to thepresent embodiment includes a substrate for electrode for electrolysis10 and a pair of first layers 20 with which both the surfaces of thesubstrate for electrode for electrolysis 10 are covered. The entiresubstrate for electrode for electrolysis 10 is preferably covered withthe first layers 20. This covering is likely to improve the catalystactivity and durability of the electrode for electrolysis. One firstlayer 20 may be laminated only on one surface of the substrate forelectrode for electrolysis 10.

Also as shown in FIG. 119, the surfaces of the first layers 20 may becovered with second layers 30. The entire first layers 20 are preferablycovered by the second layers 30. Alternatively, one second layer 30 maybe laminated only one surface of the first layer 20.

(Substrate for Electrode for Electrolysis)

As the substrate for electrode for electrolysis 10, for example, nickel,nickel alloys, stainless steel, or valve metals including titanium canbe used, although not limited thereto. The substrate 10 preferablycontains at least one element selected from nickel (Ni) and titanium(Ti).

When stainless steel is used in an alkali aqueous solution of a highconcentration, iron and chromium are eluted and the electricalconductivity of stainless steel is of the order of one-tenth of that ofnickel. In consideration of the foregoing, a substrate containing nickel(Ni) is preferable as the substrate for electrode for electrolysis.

Alternatively, when the substrate for electrode for electrolysis 10 isused in a salt solution of a high concentration near the saturationunder an atmosphere in which chlorine gas is generated, the material ofthe substrate for electrode 10 is also preferably titanium having highcorrosion resistance.

The form of the substrate for electrode for electrolysis 10 is notparticularly limited, and a form suitable for the purpose can beselected. As the form, any of a perforated metal, nonwoven fabric,foamed metal, expanded metal, metal porous foil formed byelectroforming, so-called woven mesh produced by knitting metal lines,and the like can be used. Among these, a perforated metal or expandedmetal is preferable. Electroforming is a technique for producing a metalthin film having a precise pattern by using photolithography andelectroplating in combination. It is a method including forming apattern on a substrate with a photoresist and electroplating the portionnot protected by the resist to provide a metal thin film.

As for the form of the substrate for electrode for electrolysis, asuitable specification depends on the distance between the anode and thecathode in the electrolyzer. In the case where the distance between theanode and the cathode is finite, an expanded metal or perforated metalform can be used, and in the case of a so-called zero-gap baseelectrolyzer, in which the ion exchange membrane is in contact with theelectrode, a woven mesh produced by knitting thin lines, wire mesh,foamed metal, metal nonwoven fabric, expanded metal, perforated metal,metal porous foil, and the like can be used, although not limitedthereto.

Examples of the substrate for electrode for electrolysis 10 include ametal porous foil, a wire mesh, a metal nonwoven fabric, a perforatedmetal, an expanded metal, and a foamed metal.

As a plate material before processed into a perforated metal or expandedmetal, rolled plate materials and electrolytic foils are preferable. Anelectrolytic foil is preferably further subjected to a plating treatmentby use of the same element as the base material thereof, as thepost-treatment, to thereby form asperities on one or both of thesurfaces.

The thickness of the substrate for electrode for electrolysis 10 is, asmentioned above, preferably 300 μm or less, more preferably 205 μm orless, further preferably 155 μm or less, further more preferably 135 μmor less, even further more preferably 125 μm or less, still morepreferably 120 μm or less, even still more preferably 100 μm or less,and further still more preferably 50 μm or less from the viewpoint of ahandling property and economy. The lower limit value is not particularlylimited, but is 1 μm, for example, preferably 5 μm, more preferably 15μm.

In the substrate for electrode for electrolysis, the residual stressduring processing is preferably relaxed by annealing the substrate forelectrode for electrolysis in an oxidizing atmosphere. It is preferableto form asperities using a steel grid, alumina powder, or the like onthe surface of the substrate for electrode for electrolysis followed byan acid treatment to increase the surface area thereof, in order toimprove the adhesion to a catalyst layer with which the surface iscovered. Alternatively, it is preferable to give a plating treatment byuse of the same element as the substrate to increase the surface area.

To bring the first layer 20 into close contact with the surface of thesubstrate for electrode for electrolysis 10, the substrate for electrodefor electrolysis 10 is preferably subjected to a treatment of increasingthe surface area. Examples of the treatment of increasing the surfacearea include a blast treatment using a cut wire, steel grid, aluminagrid or the like, an acid treatment using sulfuric acid or hydrochloricacid, and a plating treatment using the same element to that of thesubstrate. The arithmetic average surface roughness (Ra) of thesubstrate surface is not particularly limited, but is preferably 0.05 μmto 50 μm, more preferably 0.1 to 10 μm, further preferably 0.1 to 8 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as an anode for common salt electrolysis will bedescribed.

(First Layer)

In FIG. 119, a first layer 20 as a catalyst layer contains at least oneof ruthenium oxides, iridium oxides, and titanium oxides. Examples ofthe ruthenium oxide include RuO₂. Examples of the iridium oxide includeIrO₂. Examples of the titanium oxide include TiO₂. The first layer 20preferably contains two oxides: a ruthenium oxide and a titanium oxideor three oxides: a ruthenium oxide, an iridium oxide, and a titaniumoxide. This makes the first layer 20 more stable and additionallyimproves the adhesion with the second layer 30.

When the first layer 20 contains two oxides: a ruthenium oxide and atitanium oxide, the first layer 20 contains preferably 1 to 9 mol, morepreferably 1 to 4 mol of the titanium oxide based on 1 mol of theruthenium oxide contained in the first layer 20. With the compositionratio of the two oxides in this range, the electrode for electrolysis100 exhibits excellent durability.

When the first layer 20 contains three oxides: a ruthenium oxide, aniridium oxide, and a titanium oxide, the first layer 20 containspreferably 0.2 to 3 mol, more preferably 0.3 to 2.5 mol of the iridiumoxide based on 1 mol of the ruthenium oxide contained in the first layer20. The first layer 20 contains preferably 0.3 to 8 mol, more preferably1 to 7 mol of the titanium oxide based on 1 mol of the ruthenium oxidecontained in the first layer 20. With the composition ratio of the threeoxides in this range, the electrode for electrolysis 100 exhibitsexcellent durability.

When the first layer 20 contains at least two of a ruthenium oxide, aniridium oxide, and a titanium oxide, these oxides preferably form asolid solution. Formation of the oxide solid solution allows theelectrode for electrolysis 100 to exhibit excellent durability.

In addition to the compositions described above, oxides of variouscompositions can be used as long as at least one oxide of a rutheniumoxide, an iridium oxide, and titanium oxide is contained. For example,an oxide coating called DSA(R), which contains ruthenium, iridium,tantalum, niobium, titanium, tin, cobalt, manganese, platinum, and thelike, can be used as the first layer 20.

The first layer 20 need not be a single layer and may include aplurality of layers. For example, the first layer 20 may include a layercontaining three oxides and a layer containing two oxides. The thicknessof the first layer 20 is preferably 0.05 to 10 more preferably 0.1 to 8μm.

(Second Layer)

The second layer 30 preferably contains ruthenium and titanium. Thisenables the chlorine overvoltage immediately after electrolysis to befurther lowered.

The second layer 30 preferably contains a palladium oxide, a solidsolution of a palladium oxide and platinum, or an alloy of palladium andplatinum. This enables the chlorine overvoltage immediately afterelectrolysis to be further lowered.

A thicker second layer 30 can maintain the electrolytic performance fora longer period, but from the viewpoint of economy, the thickness ispreferably 0.05 to 3 μm.

Next, a case where the electrode for electrolysis in the presentembodiment is used as a cathode for common salt electrolysis will bedescribed.

(First Layer)

Examples of components of the first layer 20 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 20 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal.

When the first layer 20 contains at least one of platinum group metals,platinum group metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal, the platinum group metals, platinumgroup metal oxides, platinum group metal hydroxides, and alloyscontaining a platinum group metal preferably contain at least oneplatinum group metal of platinum, palladium, rhodium, ruthenium, andiridium.

As the platinum group metal, platinum is preferably contained.

As the platinum group metal oxide, a ruthenium oxide is preferablycontained.

As the platinum group metal hydroxide, a ruthenium hydroxide ispreferably contained.

As the platinum group metal alloy, an alloy of platinum with nickel,iron, and cobalt is preferably contained.

Further, as required, an oxide or hydroxide of a lanthanoid element ispreferably contained as a second component. This allows the electrodefor electrolysis 100 to exhibit excellent durability.

As the oxide or hydroxide of a lanthanoid element, at least one selectedfrom lanthanum, cerium, praseodymium, neodymium, promethium, samarium,europium, gadolinium, terbium, and dysprosium is preferably contained.

Further, as required, an oxide or hydroxide of a transition metal ispreferably contained as a third component.

Addition of the third component enables the electrode for electrolysis100 to exhibit more excellent durability and the electrolysis voltage tobe lowered.

Examples of a preferable combination include ruthenium only,ruthenium+nickel, ruthenium+cerium, ruthenium+lanthanum,ruthenium+lanthanum+platinum, ruthenium+lanthanum+palladium,ruthenium+praseodymium, ruthenium+praseodymium+platinum,ruthenium+praseodymium+platinum+palladium, ruthenium+neodymium,ruthenium+neodymium+platinum, ruthenium+neodymium+manganese,ruthenium+neodymium+iron, ruthenium+neodymium+cobalt,ruthenium+neodymium+zinc, ruthenium+neodymium+gallium,ruthenium+neodymium+sulfur, ruthenium+neodymium+lead,ruthenium+neodymium+nickel, ruthenium+neodymium+copper,ruthenium+samarium, ruthenium+samarium+manganese,ruthenium+samarium+iron, ruthenium+samarium+cobalt,ruthenium+samarium+zinc, ruthenium+samarium+gallium,ruthenium+samarium+sulfur, ruthenium+samarium+lead,ruthenium+samarium+nickel, platinum+cerium, platinum+palladium+cerium,platinum+palladium+lanthanum+cerium, platinum+iridium,platinum+palladium, platinum+iridium+palladium,platinum+nickel+palladium, platinum+nickel+ruthenium, alloys of platinumand nickel, alloys of platinum and cobalt, and alloys of platinum andiron.

When platinum group metals, platinum group metal oxides, platinum groupmetal hydroxides, and alloys containing a platinum group metal are notcontained, the main component of the catalyst is preferably nickelelement.

At least one of nickel metal, oxides, and hydroxides is preferablycontained.

As the second component, a transition metal may be added. As the secondcomponent to be added, at least one element of titanium, tin,molybdenum, cobalt, manganese, iron, sulfur, zinc, copper, and carbon ispreferably contained.

Examples of a preferable combination include nickel+tin,nickel+titanium, nickel+molybdenum, and nickel+cobalt.

As required, an intermediate layer can be placed between the first layer20 and the substrate for electrode for electrolysis 10. The durabilityof the electrode for electrolysis 100 can be improved by placing theintermediate layer.

As the intermediate layer, those having affinity to both the first layer20 and the substrate for electrode for electrolysis 10 are preferable.As the intermediate layer, nickel oxides, platinum group metals,platinum group metal oxides, and platinum group metal hydroxides arepreferable. The intermediate layer can be formed by applying and bakinga solution containing a component that forms the intermediate layer.Alternatively, a surface oxide layer also can be formed by subjecting asubstrate to a thermal treatment at a temperature of 300 to 600° C. inan air atmosphere. Besides, the layer can be formed by a known methodsuch as a thermal spraying method and ion plating method.

(Second Layer)

Examples of components of the first layer 30 as the catalyst layerinclude metals such as C, Si, P, S, Al, Ti, V, Cr, Mn, Fe, Co, Ni, Cu,Zn, Y, Zr, Nb, Mo, Ru, Rh, Pd, Ag, Cd, In, Sn, Ta, W, Re, Os, Ir, Pt,Au, Hg, Pb, Bi, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb,and Lu, and oxides and hydroxides of the metals.

The first layer 30 may or may not contain at least one of platinum groupmetals, platinum group metal oxides, platinum group metal hydroxides,and alloys containing a platinum group metal. Examples of a preferablecombination of elements contained in the second layer include thecombinations enumerated for the first layer. The combination of thefirst layer and the second layer may be a combination in which thecompositions are the same and the composition ratios are different ormay be a combination of different compositions.

As the thickness of the catalyst layer, the total thickness of thecatalyst layer formed and the intermediate layer is preferably 0.01 μmto 20 μm. With a thickness of 0.01 μm or more, the catalyst layer cansufficiently serve as the catalyst. With a thickness of 20 μm or less,it is possible to form a robust catalyst layer that is unlikely to falloff from the substrate. The thickness is more preferably 0.05 μm to 15μm. The thickness is more preferably 0.1 μm to 10 μm. The thickness isfurther preferably 0.2 μm to 8 μm.

The thickness of the electrode, that is, the total thickness of thesubstrate for electrode for electrolysis and the catalyst layer ispreferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less in respect of the handling property of theelectrode. A thickness of 135 μm or less can provide a good handlingproperty. Further, from a similar viewpoint as above, the thickness ispreferably 130 μm or less, more preferably less than 130 μm, furtherpreferably 115 μm or less, further more preferably 65 μm or less. Thelower limit value is not particularly limited, but is preferably 1 μm ormore, more preferably 5 μm or more for practical reasons, morepreferably 20 μm or more. The thickness of the electrode can bedetermined by measurement with a digimatic thickness gauge (MitutoyoCorporation, minimum scale 0.001 mm). The thickness of the substrate forelectrode for electrolysis is measured in the same manner as thethickness of the electrode. The thickness of the catalyst layer can bedetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode.

In method for producing an electrolyzer according to the presentembodiment, the electrode for electrolysis preferably contains at leastone catalytic component selected from the group consisting of Ru, Rh,Pd, Ir, Pt, Au, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Y, Zr, Nb, Mo, Ag,Ta, W, Re, Os, Al, In, Sn, Sb, Ga, Ge, B, C, N, O, Si, P, S, La, Ce, Pr,Nd, Pm, Sm, Eu, Gd, Tb, and Dy from the viewpoint of achievingsufficient electrolytic performance.

In the present embodiment, from the viewpoint that the electrode forelectrolysis, if being an electrode having a broad elastic deformationregion, can provide a better handling property and has a better adhesiveforce to a membrane such as an ion exchange membrane and a microporousmembrane, a degraded electrode, a feed conductor having no catalystcoating, and the like, the thickness of the electrode for electrolysisis preferably 315 μm or less, more preferably 220 μm or less, furtherpreferably 170 μm or less, further more preferably 150 μm or less,particularly preferably 145 μm or less, still more preferably 140 μm orless, even still more preferably 138 μm or less, further still morepreferably 135 μm or less. A thickness of 135 μm or less can provide agood handling property. Further, from a similar viewpoint as above, thethickness is preferably 130 μm or less, more preferably less than 130μm, further preferably 115 μm or less, further more preferably 65 μm orless. The lower limit value is not particularly limited, but ispreferably 1 μm or more, more preferably 5 μm or more for practicalreasons, more preferably 20 μm or more. In the present embodiment,“having a broad elastic deformation region” means that, when anelectrode for electrolysis is wound to form a wound body, warpagederived from winding is unlikely to occur after the wound state isreleased. The thickness of the electrode for electrolysis refers to,when a catalyst layer mentioned below is included, the total thicknessof both the substrate for electrode for electrolysis and the catalystlayer.

(Method for Producing Electrode for Electrolysis)

Next, one embodiment of the method for producing the electrode forelectrolysis 100 will be described in detail.

In the present embodiment, the electrode for electrolysis 100 can beproduced by forming the first layer 20, preferably the second layer 30,on the substrate for electrode for electrolysis by a method such asbaking of a coating film under an oxygen atmosphere (pyrolysis), orplating, plating, or thermal spraying. The production method of thepresent embodiment as mentioned can achieve a high productivity of theelectrode for electrolysis 100. Specifically, a catalyst formed on thesubstrate for electrode for electrolysis by an application step ofapplying a coating liquid containing a catalyst, a drying step of cryingthe coating liquid, and a pyrolysis step of performing pyrolysis.Pyrolysis herein means that a metal salt which is to be a precursor isdecomposed by heating into a metal or metal oxide and a gaseoussubstance. The decomposition product depends on the metal species to beused, type of the salt, and the atmosphere under which pyrolysisperformed, and many metals tend to form oxides in an oxidizingatmosphere. In an industrial process of producing an electrode,pyrolysis is usually performed in air, and a metal oxide or a metalhydroxide is formed in many cases.

(Formation of First Layer of Anode) (Application Step)

The first layer 20 is obtained by applying a solution in which at leastone metal salt of ruthenium, iridium, and titanium is dissolved (firstcoating liquid) onto the substrate for electrode for electrolysis andthen pyrolyzing (baking) the coating liquid in the presence of oxygen.The content of ruthenium, iridium, and titanium in the first coatingliquid is substantially equivalent to that of the first layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration in thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis100, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a long period as required can further improve thestability of the first layer 20.

(Formation of Second Layer)

The second layer 30, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound and aplatinum compound or a solution containing a ruthenium compound and atitanium compound (second coating liquid) onto the first layer 20 andthen pyrolyzing the coating liquid in the presence of oxygen.

(Formation of First Layer of Cathode by Pyrolysis Method) (ApplicationStep)

The first layer 20 is obtained by applying a solution in which metalsalts various combination are dissolved (first coating liquid) onto thesubstrate for electrode for electrolysis and then pyrolyzing (baking)the coating liquid in the presence of oxygen. The content of the metalin the first coating liquid is substantially equivalent to that in thefirst layer 20.

The metal salts may be chlorides, nitrates, sulfates, metal alkoxides,and any other forms. The solvent of the first coating liquid can beselected depending on the type of the metal salt, and water and alcoholssuch as butanol can be used. As the solvent, water or a mixed solvent ofwater and an alcohol is preferable. The total metal concentration thefirst coating liquid in which the metal salts are dissolved is notparticularly limited, but is preferably in the range of 10 to 150 g/L inassociation with the thickness of the coating film to be formed by asingle coating.

Examples of a method used as the method for applying the first coatingliquid onto the substrate for electrode for electrolysis 10 include adipping method of immersing the substrate for electrode for electrolysis10 in the first coating liquid, a method of brushing the first coatingliquid, a roll method using a sponge roll impregnated with the firstcoating liquid, and an electrostatic coating method in which thesubstrate for electrode for electrolysis 10 and the first coating liquidare oppositely charged and spraying is performed. Among these,preferable is the roll method or electrostatic coating method, which hasan excellent industrial productivity.

(Drying Step and Pyrolysis Step)

After being applied onto the substrate for electrode for electrolysis10, the first coating liquid is dried at a temperature of 10 to 90° C.and pyrolyzed in a baking furnace heated to 350 to 650° C. Between thedrying and pyrolysis, preliminary baking at 100 to 350° C. may beperformed as required. The drying, preliminary baking, and pyrolysistemperature can be appropriately selected depending on the compositionand the solvent type of the first coating liquid. A longer time periodof pyrolysis per step is preferable, but from the viewpoint of theproductivity of the electrode, 3 to 60 minutes is preferable, 5 to 20minutes is more preferable.

The cycle of application, drying, and pyrolysis described above isrepeated to form a covering (the first layer 20) to a predeterminedthickness. After the first layer 20 is formed and then furtherpost-baked for a lone period as required can further improve thestability of the first layer 20.

(Formation of Intermediate Layer)

The intermediate layer, which is formed as required, is obtained, forexample, by applying a solution containing a palladium compound orplatinum compound (second coating liquid) onto the substrate and thenpyrolyzing the coating liquid in the presence of oxygen. Alternatively,a nickel oxide intermediate layer may be formed on the substrate surfaceonly by heating the substrate, without applying a solution thereon.

(Formation of First Layer of Cathode by Ion Plating)

The first layer 20 can be formed also by ion plating.

An example includes a method in which the substrate is fixed in achamber and the metal ruthenium target is irradiated with an electronbeam. Evaporated metal ruthenium particles are positively charged inplasma in the chamber to deposit on the substrate negatively charged.The plasma atmosphere is argon and oxygen, and ruthenium deposits asruthenium oxide on the substrate.

(Formation of First Layer of Cathode by Plating)

The first layer 20 can be formed also by a plating method.

As an example, when the substrate is used as the cathode and subjectedto electrolytic plating in an electrolyte solution containing, nickeland tin, alloy plating of nickel and tin can be formed.

(Formation of First Layer of Cathode by Thermal spraying)

The first layer 20 can be formed also by thermal spraying.

As an example, plasma spraying nickel oxide particles onto the substratecan form a catalyst layer in which metal nickel and nickel oxide aremixed.

Hereinafter, an ion exchange membrane according to one aspect of themembrane will be described in detail.

[Ion Exchange Membrane]

The ion exchange membrane is not particularly limited as long as themembrane can be laminated with the electrode for electrolysis, andvarious ion exchange membranes may be employed. In the method forproducing an electrolyzer according to the present embodiment, an ionexchange membrane that has a membrane body containing a hydrocarbonpolymer or fluorine-containing polymer having an ion exchange group anda coating layer provided on at least one surface of the membrane body ispreferably used. It is preferable that the coating layer containinorganic material particles and a binder and the specific surface areaof the coating layer be 0.1 to 10 m²/g. The ion exchange membrane havingsuch a structure has a small influence of gas generated duringelectrolysis on electrolytic performance and tends to exert stableelectrolytic performance.

The membrane of a perfluorocarbon polymer into which an ion exchangegroup is introduced described above includes either one of a sulfonicacid layer having an ion exchange group derived from a sulfo group (agroup represented by —SO₃ ⁻, hereinbelow also referred to as a “sulfonicacid group”) or a carboxylic acid layer having an ion exchange groupderived from a carboxyl group (a group represented by —CO₂ ⁻,hereinbelow also referred to as a “carboxylic acid group”). From theviewpoint of strength and dimension stability, reinforcement corematerials are preferably further included.

The inorganic material particles and binder will be described in detailin the section of description of the coating layer below.

FIG. 120 illustrates a cross-sectional schematic view showing oneembodiment of an ion exchange membrane. An ion exchange membrane 1 has amembrane body 10 containing a hydrocarbon polymer or fluorine-containingpolymer having an ion exchange group and coating layers 11 a and 11 bformed on both the surfaces of the membrane body 10.

In the ion exchange membrane 1, the membrane body 10 comprises asulfonic acid layer 3 having an ion exchange group derived from a sulfogroup (a group represented by hereinbelow also referred to as a“sulfonic acid group”) and a carboxylic acid layer 2 having an ionexchange group derived from a carboxyl group group represented by —CO₂—,hereinbelow also referred to as a “carboxylic acid group”), and thereinforcement core materials 4 enhance the strength and dimensionstability. The ion exchange membrane 1, as comprising the sulfonic acidlayer 3 and the carboxylic acid layer 2, is suitably used as an anionexchange membrane.

The ion exchange membrane may include either one of the sulfonic acidlayer and the carboxylic acid layer. The ion exchange membrane may notbe necessarily reinforced by reinforcement core materials, and thearrangement of the reinforcement core materials is not limited to theexample in FIG. 120.

(Membrane Body)

First, the membrane body 10 constituting the ion exchange membrane 1will be described.

The membrane body 10 should be one that has a function of selectivelyallowing cations to permeate and comprises a hydrocarbon polymer or afluorine-containing polymer having an ion exchange group. Itsconfiguration and material are not particularly limited, and preferredones can be appropriately selected.

The hydrocarbon polymer or fluorine-containing polymer having an ionexchange group in the membrane body 10 can be obtained from ahydrocarbon polymer or fluorine-containing polymer having an ionexchange group precursor capable of forming an ion exchange group byhydrolysis or the like. Specifically, for example, after a polymercomprising a main chain of a fluorinated hydrocarbon, having, as apendant side chain, a group convertible into an ion exchange group byhydrolysis or the like (ion exchange group precursor), and beingmelt-processable (hereinbelow, referred to as the “fluorine-containingpolymer (a)” in some cases) is used to prepare a precursor of themembrane body 10, the membrane body 10 can be obtained by converting theion exchange group precursor into an ion exchange group.

The fluorine-containing polymer (a) can be produced, for example, bycopolymerizing at least one monomer selected from the following firstgroup and at least one monomer selected from the following second groupand/or the following third group. The fluorine-containing polymer (a)can be also produced by homopolymerization of one monomer selected fromany of the following first group, the following second group, and thefollowing third group.

Examples of the monomers of the first group include vinyl fluoridecompounds. Examples of the vinyl fluoride compounds include vinylfluoride, tetrafluoroethylene, hexafluoropropylene, vinylidene fluoride,trifluoroethylene, chlorotrifluoroethylene, and perfluoro alkyl vinylethers. Particularly when the ion exchange membrane is used as amembrane for alkali electrolysis, the vinyl fluoride compound preferablya perfluoro monomer, and a perfluoro monomer selected from the groupconsisting of tetrafluoroethylene, hexafluoropropylene, and perfluoroalkyl vinyl ethers is preferable.

Examples of the monomers of the second group include vinyl compoundshaving a functional group convertible into a carboxylic acid-type ionexchange group (carboxylic acid group). Examples of the vinyl compoundshaving a functional group convertible into a carboxylic acid groupinclude monomers represented by CF₂═CF(OCF₂CYF)₂—O(CZF)_(t)—COOR,wherein s represents an integer of 0 to 2, t represents an integer of 1to 12, Y and Z each independently represent F or CF₃, and R represents alower alkyl group (a lower alkyl group is an alkyl group having 1 to 3carbon atoms, for example).

Among these, compounds represented byCF₂═CF(OCF₂CYF)_(n)—O(CF₂)_(m)—COOR are preferable. Wherein n representsan integer of 0 to 2, m represents an integer of 1 to 4, Y represents For CF₃, and R represents CH₃, C₂H₅, or C₃H₇.

When the ion exchange membrane is used as a cation exchange membrane foralkali electrolysis, a perfluoro compound is preferably at least used asthe monomer, but the alkyl group (see the above R) of the ester group islost from the polymer at the time of hydrolysis, and therefore the alkylgroup (R) need not be a perfluoroalkyl group in which all hydrogen atomsare replaced by fluorine atoms.

Of the above monomers, the monomers represented below are morepreferable as the monomers of the second group:

CF₂═CFOCF₂—CF(CF₃)OCF₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₂COOCH₃,

CF₂═CF[OCF₂—CF(CF₃)]₂O(CF₂)₂COOCH₃,

CF₂═CFOCF₂CF(CF₃)O(CF₂)₃COOCH₃,

CF₂═CFO(CF₂)₂COOCH₃, and

CF₂═CFO(CF₂)₃COOCH₃.

Examples of the monomers of the third group include vinyl compoundshaving a functional group convertible into a sulfone-type ion exchangegroup (sulfonic acid group). As the vinyl compounds having a functionalgroup convertible into a sulfonic acid group, for example, monomersrepresented by CF₂═CFO—X—CF₂—SO₂F are preferable, wherein X represents aperfluoroalkylene group. Specific examples of these include the monomersrepresented below:

CF₂═CFOCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F,

CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F,

CF₂═CF(CF₂)₂SO₂F,

CF₂═CFO[CF₂CF(CF₃)O]₂CF₂CF₂SO₂F, and

CF₂═CFOCF₂CF(CF₂OCF₃)OCF₂CF₂SO₂F.

Among these, CF₂═CFOCF₂CF(CF₃)OCF₂CF₂CF₂SO₂F andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F are more preferable.

The copolymer obtained from these monomers can be produced by apolymerization method developed for homopolymerization andcopolymerization of ethylene fluoride, particularly a generalpolymerization method used for tetrafluoroethylene. For example, in anon-aqueous method, a polymerization reaction can be performed in thepresence of a radical polymerization initiator such as a perfluorocarbonperoxide or an azo compound under the conditions of a temperature of 0to 200° C. and a pressure of 0.1 to 20 MPa using an inert solvent suchas a perfluorohydrocarbon or a chlorofluorocarbon.

In the above copolymerization, the type of combination of the abovemonomers and their proportion are not particularly limited and areselected and determined depending on the type and amount of thefunctional group desired to be imparted to the fluorine-containingpolymer to be obtained. For example, when a fluorine-containing polymercontaining only a carboxylic acid group is formed, at least one monomershould be selected from each of the first group and the second groupdescribed above and copolymerized. In addition, when afluorine-containing polymer containing only a sulfonic acid group isformed, at least one monomer should be selected from each of the firstgroup and the third group and copolymerized. Further, when afluorine-containing polymer having a carboxylic acid group and asulfonic acid group is formed, at least one monomer should be selectedfrom each of the first group, the second group, and the third groupdescribed above and copolymerized. In this case, the targetfluorine-containing polymer can be obtained also by separately preparinga copolymer comprising the monomers of the first group and the secondgroup described above and a copolymer comprising the monomers of thefirst group and the third group described above, and then mixing thecopolymers. The mixing proportion of the monomers is not particularlylimited, and when the amount of the functional groups per unit polymeris increased, the proportion of the monomers selected from the secondgroup and the third group described above should be increased.

The total ion exchange capacity of the fluorine-containing copolymer isnot particularly limited, but is preferably 0.5 to 2.0 mg equivalent/g,more preferably 0.6 to 1.5 mg equivalent/g. The total ion exchangecapacity herein refers to the equivalent of the exchange group per unitweight of the dry resin and can be measured by neutralization titrationor the like.

In the membrane body 10 of the ion exchange membrane 1, a sulfonic acidlayer 3 containing a fluorine-containing polymer having a sulfonic acidgroup and a carboxylic acid layer 2 containing a fluorine-containingpolymer having a carboxylic acid group are laminated. By providing themembrane body 10 having such a layer configuration, selectivepermeability for cations such as sodium ions can be further improved.

The ion exchange membrane 1 is arranged in an electrolyzer such that,usually, the sulfonic acid layer 3 is located on the anode side of theelectrolyzer and the carboxylic acid layer located on the cathode sideof the electrolyzer.

The sulfonic acid layer 3 is preferably constituted by a material havinglow electrical resistance and has a membrane thickness larger than thatof the carboxylic acid layer 2 from the viewpoint of membrane strength.The membrane thickness of the sulfonic acid layer 3 is preferably 2 to25 times, more preferably 3 to 15 times that of the carboxylic acidlayer 2.

The carboxylic acid layer 2 preferably has high anion exclusionproperties even if it has a small membrane thickness. The anionexclusion properties here refer to the property of trying to hinderintrusion and permeation of anions into and through the ion exchangemembrane 1. In order to raise the anion exclusion properties, it iseffective to dispose a carboxylic acid layer having a small ion exchangecapacity to the sulfonic acid layer.

As the fluorine-containing polymer for use in the sulfonic acid layer 3,preferable is a polymer obtained by using CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂Fas the monomer of the third group.

As the fluorine-containing polymer for use in the carboxylic acid layer2, preferable is a polymer obtained by usingCF₂═CFOCF₂CF(CF₂)O(CF₂COOCH₃ as the monomer of the second group.

(Coating Layer)

The ion exchange membrane preferably has a coating layer on at least onesurface of the membrane body. As shown in FIG. 120, in the ion exchangemembrane 1, coating layers 11 a and 11 b are formed on both the surfacesof the membrane body 10.

The coating layers contain inorganic material particles and a binder.

The average particle size of the inorganic material particles ispreferably 0.90 μm or more. When the average particle size of theinorganic material particles is 0.90 μm or more, durability toimpurities is extremely improved, in addition to attachment of gas. Thatis, enlarging the average particle size of the inorganic materialparticles as well as satisfying the value of the specific surface areamentioned above can achieve a particularly marked effect. Irregularinorganic material particles are preferable because the average particlesize and specific surface area as above are satisfied. Inorganicmaterial particles obtained by melting and inorganic material particlesobtained by grinding raw ore can be used. Inorganic material particlesobtained by grinding raw ore can preferably be used.

The average particle size of the inorganic material particles can be 2μm or less. When the average particle size of the inorganic materialparticles is 2 μm or less, it is possible to prevent damage of themembrane due to the inorganic material particles. The average particlesize of the inorganic material particle is more preferably0.90 to 1.2μm.

Here, the average particle size can be measured by particle sizeanalyzer (“SALD2200”, SHIMADZU CORPORATION).

The inorganic material particles preferably have irregular shapes. Suchshapes improve resistance to impurities further. The inorganic materialparticles preferably have a broad particle size distribution.

The inorganic material particles preferably contain at least oneinorganic material selected from the group consisting of oxides of GroupIV elements in the Periodic Table, nitrides of Group IV elements in thePeriodic Table, and carbides of Group IV elements in the Periodic Table.From the viewpoint of durability, zirconium oxide particle is morepreferable.

The inorganic material particles are preferably inorganic materialparticles produced by grinding the raw ore of the inorganic materialparticles or inorganic material particles, as spherical particles havinga uniform diameter, obtained by melt-purifying the raw ore of theinorganic material particles.

Examples of means for grinding raw ore include, but are not particularlylimited to, ball mills, bead mills, colloid mills, conical mills, discmills, edge mills, grain mills, hammer mills, pellet mills, VSI mills,Wiley mills, roller mills, and jet mills. After grinding, the particlesare preferably washed. As the washing method, the particles arepreferably treated with acid. This treatment can reduce impurities suchas iron attached to the surface of the inorganic material particles.

The coating layer preferably contains a binder. The binder is acomponent that forms the coating layers by retaining the inorganicmaterial particles on the surface of the ion exchange membrane. Thebinder preferably contains a fluorine-containing polymer from theviewpoint of durability to the electrolyte solution and products fromelectrolysis.

As the binder, a fluorine-containing polymer having a carboxylic acidgroup or sulfonic acid group is more preferable, from the viewpoint ofdurability to the electrolyte solution and products from electrolysisand adhesion to the surface of the ion exchange membrane. When a coatinglayer is provided on a layer containing a fluorine-containing polymerhaving a sulfonic acid group (sulfonic acid layer), afluorine-containing polymer having a sulfonic acid group is furtherpreferably used as the binder of the coating layer. Alternatively, whena coating layer is provided on a layer containing a fluorine-containingpolymer having a carboxylic acid group (carboxylic acid layer), afluorine-containing polymer having a carboxylic acid group is furtherpreferably used as the binder of the coating layer.

In the coating layer, the content of the inorganic material particles ispreferably 40 to 90% by mass, more preferably 50 to 90% by mass. Thecontent of the binder is preferably 10 to 60% by mass, more preferably10 to 50% by mass.

The distribution density of the coating layer in the ion exchangemembrane is preferably 0.05 to 2 mg per 1 cm². When the ion exchangemembrane has asperities on the surface thereof, the distribution densityof the coating layer is preferably 0.5 to 2 mg per 1 cm².

As the method for forming the coating layer, which is not particularlylimited, a known method, can be used. An example is a method includingapplying by a spray or the like a coating liquid obtained by dispersinginorganic material particles in a solution containing, a binder.

(Reinforcement Core Materials)

The ion exchange membrane preferably has reinforcement core materialsarranged, inside the membrane body.

The reinforcement core materials are members that enhance the strengthand dimensional stability of the ion exchange membrane. By arranging thereinforcement core materials inside the membrane body, particularlyexpansion and contraction of the ion exchange membrane can be controlledin the desired range. Such an ion exchange membrane does not expand orcontract more than necessary during electrolysis and the like and canmaintain excellent dimensional stability for a long term.

The configuration of the reinforcement core materials is notparticularly limited, and, for example, the reinforcement core materialsmay be formed by spinning yarns referred to as reinforcement yarns. Thereinforcement yarns here refer to yarns that are members constitutingthe reinforcement core materials, can provide the desired dimensionalstability and mechanical strength to the ion exchange membrane, and canbe stably present in the ion exchange membrane. By using thereinforcement core materials obtained by spinning such reinforcementyarns, better dimensional stability and mechanical strength can beprovided to the ion exchange membrane.

The material the reinforcement core materials and the reinforcementyarns used for these is not particularly limited but is preferably amaterial resistant to acids, alkalis, etc., and a fiber comprising afluorine-containing polymer is preferable because long-term heatresistance and chemical resistance are required.

Examples of the fluorine-containing polymer to be used in thereinforcement core materials include polytetrafluoroethylene (PTFE),tetrafluoroethylene-perfluoroalkyl vinyl ether copolymers (PFA),tetrafluoroethylene-ethylene copolymers (ETFE),tetrafluoroethylene-hexafluoropropylene copolymers,trifluorochloroethylene-ethylene copolymers, and vinylidene fluoridepolymers (PVDF). Among these, fibers comprising polytetrafluoroethyleneare preferably used from the viewpoint of heat resistance and chemicalresistance.

The yarn diameter of the reinforcement yarns used for the reinforcementcore materials is not particularly limited, but is preferably 20 to 300deniers, more preferably 50 to 250 deniers. The weave density (fabriccount per unit length) is preferably 5 to 50/inch. The form of thereinforcement core materials is not particularly limited, for example, awoven fabric, a nonwoven fabric, and a knitted fabric are used, but ispreferably in the form of a woven fabric. The thickness of the wovenfabric to be used is preferably 30 to 250 μm, more preferably 30 to 150μm.

As the woven fabric or knitted fabric, monofilaments, multifilaments, oryarns thereof, a slit yarn, or the like can be used, and various typesof weaving methods such as a plain weave, a leno weave, a knit weave, acord weave, and a seersucker can be used.

The weave and arrangement of the reinforcement core materials in themembrane body are not particularly limited, and preferred arrangementcan be appropriately provided considering the size and form of the ionexchange membrane, physical properties desired for the ion exchangemembrane, the use environment, and the like.

For example, the reinforcement core materials may be arranged along onepredetermined direction of the membrane body, but from the viewpoint ofdimensional stability, it is preferred that the reinforcement corematerials be arranged along a predetermined first direction, and otherreinforcement core materials be arranged along a second directionsubstantially perpendicular to the first direction. By arranging theplurality of reinforcement core materials substantially orthogonallyinside the membrane body, it is possible to impart better dimensionalstability and mechanical strength in many directions. For example,arrangement in which the reinforcement core materials arranged along thelongitudinal direction (warp yarns) and the reinforcement core materialsarranged along the transverse direction (weft yarns) are woven on thesurface side of the membrane body is preferred. The arrangement is morepreferably in the form of plain weave driven and woven by allowing warpsand wefts to run over and under each other alternately, leno weave inwhich two warps are woven into wefts while twisted, basket weave drivenand woven by inserting, into two or more parallelly-arranged warps,wefts of the same number, or the like, from the viewpoint of dimensionstability, mechanical strength and easy-production.

It is preferred that particularly, the reinforcement core materials bearranged along both directions, the MD (Machine Direction) and TD(Transverse Direction) of the ion exchange membrane. In other words, thereinforcement core materials are preferably plain-woven in the MD andTD. Here, the MD refers to the direction in which the membrane body andvarious core materials (for example, the reinforcement core materials,reinforcement yarns, and sacrifice yarns described later) are conveyedin an ion exchange membrane production step described later (flowdirection), and the TD refers to the direction substantiallyperpendicular to the MD. Yarns woven along the MD are referred to as MDyarns, and yarns woven along the TD are referred to as TD yarns.Usually, the ion exchange membrane used for electrolysis is rectangular,and in many cases, the longitudinal direction is the MD, and the widthdirection is the TD. By weaving the reinforcement core materials thatare MD yarns and the reinforcement core materials that are TD yarns, itis possible to impart better dimensional stability and mechanicalstrength in many directions.

The arrangement interval of the reinforcement core materials is notparticularly limited, and preferred arrangement can be appropriatelyprovided considering physical properties desired for the ion exchangemembrane, the use environment, and the like.

The aperture ratio for the reinforcement core materials is notparticularly limited, but is preferably 30% or more, more preferably 50%or more and 90% or less. The aperture ratio is preferably 30% or morefrom the viewpoint of the electrochemical properties of the ion exchangemembrane, and preferably 90% or less from the viewpoint of themechanical strength of the ion exchange membrane.

The aperture ratio for the reinforcement core materials herein refers toa ratio of a total area of a surface through which substances such asions (an electrolyte solution and cations contained therein (e.g.,sodium ions)) can pass (B) to the area of either one surface of themembrane body (A) (B/A). The total area of the surface through whichsubstances such as ions can pass (B) can refer to the total areas ofregions in which in the ion exchange membrane, cations, an electrolyticsolution, and the like are not blocked by the reinforcement corematerials and the like contained in the ion exchange membrane.

FIG. 121 illustrates a schematic view for explaining the aperture ratioof reinforcement core materials constituting the ion exchange membrane.FIG. 121, in which a portion of the ion exchange membrane is enlarged,shows only the arrangement of the reinforcement core materials 21 and 22in the regions, omitting illustration of the other members.

By subtracting the total area of the reinforcement core materials (C)from the area of the region surrounded by the reinforcement corematerials 21 arranged along the longitudinal direction and thereinforcement core materials 22 arranged along the transverse direction,the region including the area of the reinforcement core materials (A),the total area of regions through which substances such as ions can pass(B) in the area of the above-described region (A) can be obtained. Thatis, the aperture ratio can be determined by the following formula (I):

Aperature ratio=(B)/(A)=((A)−(C))/(A)   (I)

Among the reinforcement core materials, a particularly preferred form istape yarns or highly oriented monofilaments comprising PTFE from theviewpoint of chemical resistance and heat resistance. Specifically,reinforcement core materials forming a plain weave in which 50 to 300denier tape yarns obtained by slitting a high strength porous sheetcomprising PTFE into a tape form, or 50 to 300 denier highly orientedmonofilaments comprising PTFE are used and which has a weave density of10 to 50 yarns or monofilaments/inch and has a thickness in the range of50 to 100 μm are more preferred. The aperture ratio of an ion exchangemembrane comprising such reinforcement core materials is furtherpreferably 60% or more.

Examples of the shape of the reinforcement yarns Include round yarns andtape yarns.

(Continuous Holes)

The ion exchange membrane preferably has continuous holes inside themembrane body.

The continuous holes refer to holes that can be flow paths for ionsgenerated in electrolysis and an electrolyte solution. The continuousholes, which are tubular holes formed inside the membrane body, areformed by dissolution of sacrifice core materials (or sacrifice yarns)described below The shape, diameter, or the like of the continuous holescan be controlled by selecting the shape or diameter of the sacrificecore materials (sacrifice yarns).

Forming the continuous holes inside the ion exchange membrane can ensurethe mobility of an electrolyte solution on electrolysis. The shape ofthe continuous holes is not particularly limited, but may be the shapesacrifice core materials to be used for formation of the continuousholes in accordance with the production method described below.

The continuous holes are preferably formed so as to alternately pass onthe anode side (sulfonic acid layer side) and the cathode side(carboxylic acid layer side) of the reinforcement core materials. Withsuch a structure, in a portion in which continuous holes are formed onthe cathode side of the reinforcement core materials, ions (e.g., sodiumions) transported through the electrolyte solution with which thecontinuous holes are filled can flow also on the cathode side of thereinforcement core materials. As a result, the flow of cations is notinterrupted, and thus, it is possible to further reduce the electricalresistance of the ion exchange membrane.

The continuous holes may be formed along only one predetermineddirection of the membrane body constituting the ion exchange membrane,but are preferably formed in both the longitudinal direction and thetransverse direction of the membrane body from the viewpoint ofexhibiting more stable electrolytic performance.

[Production Method]

A suitable example of a method for producing an ion exchange membraneincludes a method including the following steps (1) to (6):

Step (1): the step of producing a fluorine-containing polymer having anion exchange group or an ion exchange group precursor capable of formingan ion exchange group by hydrolysis,

Step (2): the step of weaving at least a plurality of reinforcement corematerials, as required, and sacrifice yarns having a property ofdissolving in an acid or an alkali, and forming continuous holes, toobtain a reinforcing material in which the sacrifice yarns are arrangedbetween the reinforcement core materials adjacent to each other,

Step (3): the step of forming into a film the above fluorine-containingpolymer having an ion exchange group or an ion exchange group precursorcapable of forming an ion exchange group by hydrolysis,

Step (4): the step of embedding the above reinforcing materials, asrequired, in the above film to obtain a membrane body inside which thereinforcing materials are arranged,

Step (5): the step of hydrolyzing the membrane body obtained in the step(4) (hydrolysis step), and

Step (6): the step of providing a coating layer on the membrane bodyobtained in the step (5) (application step).

Hereinafter, each of the steps will be described in detail.

Step (1): Step of Producing Fluorine-Containing Polymer

In the step (1), raw material monomers described in the first group tothe third group above are used to produce a fluorine-containing polymer.In order to control the ion exchange capacity of the fluorine-containingpolymer, the mixture ratio of the raw material monomers should beadjusted in the production of the fluorine-containing polymer formingthe layers.

Step (2): Step of Producing Reinforcing Materials

The reinforcing material is a woven fabric obtained weavingreinforcement yarns or the like. The reinforcing material is embedded inthe membrane to thereby form reinforcement core materials. When an ionexchange membrane having continuous holes is formed, sacrifice yarns areadditionally woven into the reinforcing material. The amount of thesacrifice yarns contained in this case is preferably 10 to 80% by mass,more preferably 30 to 70% by mass based on the entire reinforcingmaterial. Weaving the sacrifice yarns can also prevent yarn slippage ofthe reinforcement core materials.

As the sacrifice yarns, which have solubility in the membrane productionstep or under an electrolysis environment, rayon, polyethyleneterephthalate (PET), cellulose, polyamide, and the like are used.Monofilaments or multifilaments having a thickness of 20 to 50 deniersand comprising polyvinyl alcohol and the like are also preferred.

In the step (2), the aperture ratio, arrangement of the continuousholes, and the like can be controlled by adjusting the arrangement ofthe reinforcement core materials and the sacrifice yarns.

Step (3): Step of Film Formation

In the step (3), the fluorine-containing polymer obtained in the step(1) is formed into a film by using an extruder. The film may be asingle-layer configuration, a two-layer configuration of a sulfonic acidlayer and a carboxylic acid layer as mentioned above, or a multilayerconfiguration of three layers or more.

Examples of the film forming method include the following:

a method in which a fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group areseparately formed into films; and

a method in which fluorine-containing polymer having a carboxylic acidgroup and a fluorine-containing polymer having a sulfonic acid group arecoextruded into a composite film.

The number of each film may be more than one. Coextrusion of differentfilms is preferred because of its contribution to an increase in theadhesive strength in the interface.

Step (4): Step of Obtaining Membrane Body

In the step (4), the reinforcing material obtained in the step (2) isembedded in the film obtained in the step (3) to provide a membrane bodyincluding the reinforcing material therein.

Preferable examples of the method for forming a membrane body include amethod in which a fluorine-containing polymer having a carboxylic acidgroup precursor (e.g., carboxylate functional group) (hereinafter, alayer comprising the same is referred to as the first layer) located onthe cathode side and a fluorine-containing, polymer having a sulfonicacid group precursor (e.g., sulfonyl fluoride functional group)(hereinafter, a layer comprising the same is referred to as the secondlayer) are formed into a film by a coextrusion method, and, by using aheat source and a vacuum source as required, a reinforcing material andthe second layer/first layer composite film are laminated in this orderon breathable heat-resistant release paper on a flat plate or drumhaving many pores on the surface thereof and integrated at a temperatureat which each polymer melts while air among each of the layers wasevacuated by reduced pressure; and (ii) a method in which, in additionto the second layer/first layer composite film, a fluorine-containingpolymer having a sulfonic acid group precursor is singly formed into afilm (the third layer) in advance, and, by using a heat source and avacuum source as required, the third layer film, the reinforcement corematerials, and the composite film comprising the second layer/firstlayer are laminated in this order on breathable heat-resistant releasepaper on a flat plate or drum having many pores on the surface thereofand integrated at a temperature at which each polymer melts while airamong each of the layers was evacuated by reduced pressure.

Coextrusion of the first layer and the second layer herein contributesto an increase in the adhesive strength at the interface.

The method including integration under a reduced pressure ischaracterized by making the third layer on the reinforcing materialthicker than that of a pressure-application press method. Further, sincethe reinforcing material is fixed on the inner surface of the membranebody, the method has a property of sufficiently retaining the mechanicalstrength of the ion exchange membrane.

The variations of lamination described here are exemplary, andcoextrusion can be performed after a preferred lamination pattern (forexample, the combination of layers) is appropriately selectedconsidering the desired layer configuration of the membrane body andphysical properties, and the like.

For the purpose of further improving the electric properties of the ionexchange membrane, it is also possible to additionally interpose afourth layer comprising a fluorine-containing polymer having both acarboxylic acid group precursor and a sulfonic acid group precursorbetween the first layer and the second layer or to use a fourth layercomprising a fluorine-containing polymer having both a carboxylic acidgroup precursor and a sulfonic acid group precursor instead of thesecond layer.

The method for forming the fourth layer may be a method in which afluorine-containing polymer having a carboxylic acid group precursor anda fluorine-containing polymer having a sulfonic acid group precursor areseparately produced and then mixed or may be a method in which a monomerhaving a carboxylic acid group precursor and a monomer having a sulfonicacid group precursor are copolymerized.

When the fourth layer is used as a component of the ion exchangemembrane, a coextruded film of the first layer and the fourth layer isformed, in addition to this, the third layer and the second layer areseparately formed into films, and lamination may be performed by themethod mentioned above. Alternatively, the three layers of the firstlayer/fourth layer/second layer may be simultaneously formed into a filmby coextrusion.

In this case, the direction in which the extruded film flows is the MD.As mentioned above, it is possible to form a membrane body containing afluorine-containing polymer having an ion exchange group on areinforcing material.

Additionally, the ion exchange membrane preferably has protrudedportions composed of the fluorine-containing polymer having a sulfonicacid group, that projections, on the surface side composed of thesulfonic acid layer. As a method for forming such projections, which isnot particularly limited, a known method also can be employed includingforming projections on a resin surface. A specific example of the methodis a method of embossing the surface of the membrane body. For example,the above projections can be formed by using release paper embossed inadvance when the composite film mentioned above, reinforcing material,and the like are integrated. In the case where projections are formed byembossing, the height and arrangement density of the projections can becontrolled by controlling the emboss shape to be transferred (shape ofthe release paper).

(5) Hydrolysis Step

In the step (5), a step of hydrolyzing the membrane body obtained in thestep (4) to convert the ion exchange group precursor into an ionexchange group (hydrolysis step) is performed.

In the step (5), it is also possible to form dissolution holes in themembrane body by dissolving and removing the sacrifice yarns included inthe membrane body with acid or alkali. The sacrifice yarns may remain inthe continuous holes without being completely dissolved and removed. Thesacrifice yarns remaining in the continuous holes may be dissolved andremoved by the electrolyte solution when the ion exchange membrane issubjected to electrolysis.

The sacrifice yarn has solubility in acid or alkali in the step ofproducing an ion exchange membrane or under an electrolysis environment.The sacrifice yarns are eluted out to thereby form continuous holes atcorresponding sites.

The step (5) can be performed by immersing the membrane body obtained inthe step (4) in a hydrolysis solution containing acid or alkali. Anexample of the hydrolysis solution that can be used is a mixed solutioncontaining KOH and dimethyl sulfoxide (DMSO).

The mixed solution preferably contains KOH of 2.5 to 4.0 N and DMSO of25 to 35% by mass.

The temperature for hydrolysis is preferably 70 to 100° C. The higherthe temperature, the larger can be the apparent thickness. Thetemperature is more preferably 75 to 100° C.

The time for hydrolysis is preferably 10 to 120 minutes. The longer thetime, the larger can be the apparent thickness. The time is morepreferably 20 to 120 minutes.

The step of forming continuous holes by eluting the sacrifice yarn willbe now described in more detail. FIGS. 122(a) and (b) are schematicviews for explaining a method for forming the continuous holes of theion exchange membrane.

FIGS. 122(a) and (b) show reinforcement yarns 52, sacrifice yarns 504 a,and continuous holes 504 formed by the sacrifice yarns 504 a only,omitting illustration of the other members such as a membrane body.

First, the reinforcement yarns 52 that are to constitute reinforcementcore materials in the ion exchange membrane and the sacrifice yarns 504a for forming the continuous holes 504 in the ion exchange membrane areused as interwoven reinforcing materials. Then, in the step (5), thesacrifice yarns 504 a are eluted to form the continuous holes 504.

The above method is simple because the method for interweaving thereinforcement yarns 52 and the sacrifice yarns 504 a may be adjusteddepending on the arrangement of the reinforcement core materials andcontinuous holes in the membrane body of the ion exchange membrane.

FIG. 122(a) exemplifies the plain-woven reinforcing material in whichthe reinforcement yarns 52 and sacrifice yarns 504 a are interwovenalong both the longitudinal direction and the lateral direction in thepaper, and the arrangement of the reinforcement yarns 52 and thesacrifice yarns 504 a in the reinforcing material may be varied asrequired.

(6) Application Step

In the step (6), a coating layer can be formed by preparing a coatingliquid containing inorganic material particles obtained by grinding rawore or melting raw ore and a binder, applying the coating liquid ontothe surface of the ion exchange membrane obtained in the step (5), anddrying the coating liquid.

A preferable binder is a binder obtained by hydrolyzing afluorine-containing polymer having an ion exchange group precursor withan aqueous solution containing dimethyl sulfoxide (DMSO) and potassiumhydroxide (KOH) and then immersing the polymer in hydrochloric acid toreplace the counter of the ion exchange group by H+ (e.g., afluorine-containing polymer having a carboxyl group or sulfo group).Thereby, the polymer more likely to dissolve in water or ethanolmentioned below, which is preferable.

This binder is dissolved in a mixed solution of water and ethanol. Thevolume ratio between water and ethanol is preferably 10:1 to 1:10, morepreferably 5:1 to 1:5, further preferably 2:1 to 1:2. The inorganicmaterial particles are dispersed with a ball mill into the dissolutionliquid thus obtained to thereby provide a coating liquid. In this case,it is also possible to adjust the average particle size and the like ofthe particles by adjusting the time and rotation speed during thedispersion. The preferable amount of the inorganic material particlesand the binder to be blended is as mentioned above.

The concentration of the inorganic material particles and the binder inthe coating liquid is not particularly limited, but a thin coatingliquid is preferable. This enables uniform application onto the surfaceof the ion exchange membrane.

Additionally, a surfactant may be added to the dispersion when theinorganic material particles are dispersed. As the surfactant, nonionicsurfactants are preferable, and examples thereof include HS-210, NS-210,P-210, and E-212 manufactured by NOF CORPORATION.

The coating liquid obtained is applied onto the surface of the ionexchange membrane by spray application or roll coating to therebyprovide an ion exchange membrane.

[Microporous Membrane]

The microporous membrane of the present embodiment is not particularlylimited as long as the membrane can be formed into a laminate with theelectrode for electrolysis, as mentioned above. Various microporousmembranes may be employed.

The porosity of the microporous membrane of the present embodiment isnot particularly limited, but can be 20 to 90, for example, and ispreferably 30 to 85. The above porosity can be calculated by thefollowing formula:

Porosity=(1−(the weight of the membrane in a dried state)/(the weightcalculated from the volume calculated from the thickness, width, andlength of the membrane and the density of the membrane material))×100

The average pore size of the microporous membrane of the presentembodiment is not particularly limited, and can be 0.01 μm to 10 μm, forexample, preferably 0.05 μm to 5 μm. With respect to the average poresize, for example, the membrane is cut vertically to the thicknessdirection, and the section is observed with an FE-SEM. The average poresize can be obtained by measuring the diameter of about 100 poresobserved and averaging the measurements.

The thickness of the microporous membrane of the present embodiment isnot particularly limited, and can be 10 μm to 1000 μm, for example,preferably 50 μm to 600 μm. The above thickness can be measured by usinga micrometer (manufactures by Mitutoyo Corporation) or the like, forexample.

Specific examples of the microporous membrane as mentioned above includeZirfon Perl UTP 500 manufactured by Agfa and those described inInternational Publication No. WO 2013-183584 and InternationalPublication No. WO 2016-203701.

In the method for producing an electrolyzer according to the presentembodiment, the membrane preferably comprises a first ion exchange resinlayer and a second ion exchange resin layer having an EW (ion exchangecapacity) different from that of the first ion exchange resin layer.Additionally, the membrane preferably comprises a first ion exchangeresin layer and a second ion exchange resin layer having a functionalgroup different from that of the first ion exchange resin layer. The ionexchange capacity can be adjusted by the functional group to beintroduced, and functional groups that may be introduced are asmentioned above.

(Water Electrolysis)

The electrolyzer in the present embodiment, as an electrolyzer in thecase of electrolyzing water, has a configuration in which the ionexchange membrane in an electrolyzer for use in the case ofelectrolyzing common salt mentioned above is replaced by a microporousmembrane. The raw material to be supplied, which is water, is differentfrom that for the electrolyzer in the case of electrolyzing common saltmentioned above. As for the other components, components similar to thatof the electrolyzer in the case of electrolyzing common salt can beemployed also in the electrolyzer in the case of electrolyzing water.Since chlorine gas is generated in the anode chamber in the case ofcommon salt electrolysis, titanium is used as the material of the anodechamber, but in the case of water electrolysis, only oxygen gas isgenerated in the anode chamber. Thus, a material identical to that ofthe cathode chamber can be used. An example thereof is nickel. For anodecoating, catalyst coating for oxygen generation is suitable. Examples ofthe catalyst coating include metals, oxides, and hydroxides of theplatinum group metals and transition metal group metals. For example,elements such as platinum, iridium, palladium, ruthenium, nickel,cobalt, and iron can be used.

EXAMPLES

The present invention will be described in further detail with referenceto Examples and Comparative Examples below, but the present invention isnot limited to Examples below in any way.

<Verification of First Embodiment>

As will be described below, Experiment Examples according to the firstembodiment (in the section of <Verificaton of first embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the first embodiment in the section of <Verification offirst embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 10 to 21 asappropriate.

[Evaluation Method] (1) Opening Ratio

An electrode was cut into a size of 130 mm×100 mm. A digimatic thicknessgauge (manufactured by Mitutoyo Corporation, minimum scale 0.001 mm) wasused to calculate an average value of 10 points obtained by measuringevenly in the plane. The value was used as the thickness of theelectrode (gauge thickness) to calculate the volume. Thereafter, anelectronic balance was used to measure the mass. From the specificgravity of each metal (specific gravity of nickel=8.908 g/cm³, specificgravity of titanium=4.506 g/cm³) the opening ratio or void ratio wascalculated.

Opening ratio (Void ratio) (%)=(1−(electrode mass)/(electrodevolume×metal specific gravity))×100

(2) Mass per Unit Area (mg/cm²)

An electrode was cut into a size of 130 mm×100 mm, and the mass thereofwas measured by an electronic balance. The value was divided by the area(130 mm×100 mm) to calculate the mass per unit area.

(3) Force Applied per Unit Mass·Unit Area (1) (Adhesive Force)(N/mg·cm²))

[Method (i)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-6001 type load cell).

A 200 mm square nickel plate having a thickness of 1.2 mm was subjectedto blast processing with alumina of grain-size number 320. Thearithmetic average surface roughness (Ra) of the nickel plate after theblast treatment was 0.7 μm. For surface roughness measurement herein, aprobe type surface roughness measurement instrument SJ-310 (MitutoyoCorporation) was used. A measurement sample was placed on the surfaceplate parallel to the ground surface to measure the arithmetic averageroughness Ra under measurement conditions as described below. Themeasurement was repeated 6 times, and the average value was listed.

<Probe Shape> conical taper angle=60°, tip radius=2 μm, static measuringforce=0.75 mN

<Roughness standard> JIS2001

<Evaluation curve> R

<Filter> GAUSS

<Cutoff value λc> 0.8 mm

<Cutoff value λs> 2.5 μm

<Number of sections> 5

<Pre-running, post-running> available

This nickel plate was vertically fixed on the lower chuck of the tensileand compression testing machine.

As the membrane, an ion exchange membrane A below was used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTFE) were used (hereinafter referred to asPTFE yarns). As sacrifice yarns, yarns obtained by twisting six 35denier filaments of polyethylene terephthalate (PET) 200 times/m wereused (hereinafter referred to as PET yarns). First, in each of the TDand the MD, the PTFE yarns and the sacrifice yarns were plain-woven with24 PTFE yarns/inch so that two sacrifice yarns were arranged betweenadjacent PTFE yarns, to obtain a woven fabric. The resulting wovenfabric was pressure-bonded by a roll to obtain a woven fabric having athickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin B of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film in which the thickness of aresin A layer was 15 μm and the thickness of a resin B layer was 104 μmwas obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having a primary particle sizeof 1 μm was added to a 5% by mass ethanol solution of the acid-typeresin of the resin B and dispersed to prepare a suspension, and thesuspension was sprayed onto both the surfaces of the above compositemembrane by a suspension spray method to form coatings of zirconiumoxide on the surfaces of the composite membrane to obtain an ionexchange membrane A. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.5 mg/cm². The average particle sizewas measured by a particle size analyzer (manufactured by SHIMADZUCORPORATION, “SALD(R) 2200”).

The ion exchange membrane (membrane) obtained above was immersed in purewater for 12 hours or more and then used for the test. The membrane wasbrought into contact with the above nickel plate sufficiently moistenedwith pure water and allowed to adhere to the plate by the tension ofwater. At this time, the nickel plate and the ion exchange membrane wereplaced so as to align the upper ends thereof.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedthe upper chuck of the tensile and compression testing machine to hangthe electrode. The load applied on the testing machine at this time wasset to 0 N. The integrated piece of the stainless plates, electrode, andclips was once removed from the tensile and compression testing machine,and immersed in a vat containing pure water in order to moisten theelectrode sufficiently with pure water. Thereafter, the center of thestainless plates was clamped again by the upper chuck of the tensile andcompression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the ion exchange membrane by the surfacetension of pure water. The size of the adhesive surface at this time was130 mm in width and 110 mm in length. Pure water in a wash bottle wassprayed to the electrode and the ion exchange membrane entirely so as tosufficiently moisten the membrane and the electrode again. Thereafter, aroller formed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess pure water. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the overlapping portion ofthe electrode and the membrane reached 130 mm in width and 100 mm inlength was recorded. This measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion ofthe electrode and the ion exchange membrane and the mass of theelectrode of the portion overlapping the ion exchange membrane tocalculate the force applied per unit mass·unit area (1). The mass of theelectrode of the portion overlapping the ion exchange membrane wasdetermined through proportional calculation from the value obtained in(2) Mass per unit area (mg/cm²) described above.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was 30±5%.

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to the ion exchange membrane that adhered to avertically-fixed nickel plate via the surface tension.

A schematic view of a method for evaluating the force applied (1) isshown in FIG. 10.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(4) Force Applied per Unit Mass·Unit Area (2) (Adhesive Force)(N/mg·cm²))

[Method (ii)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-6001 type load cell).

A nickel plate identical to that in Method (i) was vertically fixed onthe lower chuck of the tensile and compression testing machine.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedby the upper chuck of the tensile and compression testing machine tohang the electrode. The load applied on the testing machine at this timewas set to 0 N. The integrated piece of the stainless plates, electrode,and clips was once removed from the tensile and compression testingmachine, and immersed in a vat containing pure water in order to moistenthe electrode sufficiently with pure water. Thereafter, the center ofthe stainless plates was clamped again by the upper chuck of the tensileand compression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the nickel plate via the surface tension of asolution. The size of the adhesive surface at this time was 130 mm inwidth and 110 mm in length. Pure water in a wash bottle was sprayed tothe electrode and the nickel plate entirely so as to sufficientlymoisten the nickel plate and the electrode again. Thereafter, a rollerformed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess solution. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the overlapping portion ofthe electrode and the nickel plate in the longitudinal direction reached100 mm was recorded. This measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion ofthe electrode and the nickel plate and the mass of the electrode of theportion overlapping the nickel plate to calculate the force applied perunit mass·unit area (2). The mass of the electrode of the portionoverlapping the membrane was determined through proportional calculationfrom the value obtained in (2) mass per unit area (mg/cm²) describedabove.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was 30±5%.

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to a vertically-fixed nickel plate via the surfacetension.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(5) Method for Evaluating Winding Around Column of 280 mm in Diameter(1) (%) (Membrane and Column)

The evaluation method (1) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square. The ion exchange membrane was immersed in purewater for 12 hours or more and then used for the test. In ComparativeExamples 10 and 11, the electrode had been integrated with the ionexchange membrane by thermal pressing, and thus, an integrated piece ofan ion exchange membrane and an electrode was provided (electrode of a130 mm square). After the ion exchange membrane was sufficientlyimmersed in pure water, the membrane was placed on the curved surface ofa plastic (polyethylene) pipe having an outer diameter of 280 mm.Thereafter, excess solution was removed with a roller formed by windinga closed-cell type EPDM sponge rubber having a thickness of 5 mm arounda vinyl chloride pipe (outer diameter: 38 mm). The roller was rolledover the ion exchange membrane from the left to the right of theschematic view shown in FIG. 11. The roller was rolled only once. Oneminute after, the proportion of a portion at which the ion exchangemembrane was brought into a close contact with the plastic pipeelectrode having an outer diameter of 280 mm was measured.

(6) Method for Evaluating Winding Around Column of 280 mm in Diameter(2) (%) (Membrane and Electrode)

The evaluation method (2) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 280 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 12 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(7) Method for Evaluating Winding Around Column of 145 mm in Diameter(3) (%) (Membrane and Electrode)

The evaluation method (3) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 145 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 13 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(8) Handling Property (Response Evaluation)

(A) The ion exchange membrane A (membrane) produced in [Method (i)] wascut into a 170 mm square, and the electrode was cut into a size of95×110 mm. The ion exchange membrane was immersed in pure water for 12hours or more and then used for the test. In each Example, the ionexchange membrane and electrode were sufficiently immersed in threesolutions: sodium bicarbonate aqueous solution, 0.1N NaOH aqueoussolution, and pure water, then laminated, and placed still on a Teflonplate. The interval between the anode cell and the cathode cell used inthe electrolytic evaluation was set at about 3 cm. The laminate placedstill was lifted, and an operation of inserting and holding the laminatetherebetween was conducted. This operation was conducted while theelectrode was checked for dislocation and dropping.

(B) The ion exchange membrane A (membrane) produced in [Method (i)] wascut into a 170 mm square, and the electrode was cut into a size of95×110 mm. The ion exchange membrane was immersed in pure water for 12hours or more and then used for the test. In each Example, the ionexchange membrane and electrode were sufficiently immersed in threesolutions: a sodium bicarbonate aqueous solution, a 0.1N NaOH aqueoussolution, and pure water, then laminated, and placed still on a Teflonplate. The adjacent two corners of the membrane portion of the laminatewere held by hands to lift the laminate so as to be vertical. The twocorners held by hands were moved from this state to be close to eachother such that the membrane was protruded or recessed. This move wasrepeated again to check the conformability of the electrode to themembrane. The results were evaluated on a four level scale of 1 to 4 onthe basis of the following indices:

1: good handling property

2: capable of being handled

3: difficult to handle

4: substantially incapable of being handled

Here, the sample of Comparative Example 5, provided in a size equivalentto that of a large electrolytic cell including an electrode in a size of1.3 m×2.5 m and an ion exchange membrane in a size of 1.5 m×2.8 m, wassubjected to handling. The evaluation result of Comparative Example 5(“3” as described below) was used as an index to evaluate the differencebetween the evaluation of the above (A) and (B) and that of thelarge-sized one. That is, in the case where the evaluation result of asmall laminate was “1” or “2”, it was judged that there was no problemin the handling property even if the laminate was provided in a largersize.

(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%), CommonSalt Concentration in Caustic Soda (ppm, on the Basis of 50%))

The electrolytic performance was evaluated by the following electrolyticexperiment.

A titanium anode cell having an anode chamber in which an anode wasprovided (anode terminal cell) and a cathode cell having a nickelcathode chamber in which a cathode was provided (cathode terminal cell)were oppositely disposed. A pair of gaskets was arranged between thecells, and a laminate (a laminate of the ion exchange membrane A and anelectrode for electrolysis) was sandwiched between the gaskets. Then,the anode cell, the gasket, the laminate, the gasket, and the cathodewere brought into close contact together to obtain an electrolytic cell,and an electrolyzer including the cell was provided.

The anode was produced by applying a mixed solution of rutheniumchloride, iridium chloride, and titanium tetrachloride onto a titaniumsubstrate subjected to blasting and acid etching treatment as thepretreatment, followed by drying and baking. The anode was fixed in theanode chamber welding. As the cathode, one described in each of Examplesand Comparative Examples was used. As the collector of the cathodechamber, a nickel expanded metal was used. The collector had a size of95 mm in length×110 mm in width. As a metal elastic body, a mattressformed by knitting nickel fine wire was used. The mattress as the metalelastic body was placed on the collector. Nickel mesh formed byplain-weaving nickel wire having a diameter of 150 μm in a sieve meshsize of 40 was placed thereover, and a string made of Teflon (R) wasused to fix the four corners of the Ni mesh to the collector. This Nimesh was used as a feed conductor. This electrolytic cell has a zero-gapstructure by use of the repulsive force of the mattress as the metalelastic body. As the gaskets, ethylene propylene diene (EPDM) rubbergaskets were used. As the membrane, the ion exchange membrane A (160 mmsquare) produced in [Method (i)] was used.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted so as to allow the temperature in each electrolytic cell toreach 90° C. Common salt electrolysis was performed at a current densityof kA/m² to measure the voltage, current density, and common saltconcentration in caustic soda. The current efficiency here is theproportion of the amount of the produced caustic soda to the passedcurrent, and when impurity ions and hydroxide ions rather than sodiumions move through the ion exchange membrane due to the passed current,the current efficiency decreases. The current efficiency was obtained bydividing the number of moles of caustic soda produced for a certain timeby the number of moles of the electrons of the current passing duringthat time. The number of moles of caustic soda was obtained byrecovering caustic soda produced by the electrolysis in a plasticcontainer and measuring its mass. As the common salt concentration incaustic soda, a value obtained by converting the caustic sodaconcentration on the basis of 50% was shown.

The specification of the electrode and the feed conductor used in eachof Examples and Comparative Examples is shown in Table 1

(11) Measurement of Thickness of Catalytic Layer, Substrate forElectrode for Electrolysis, and Thickness of Electrode

For the thickness of the substrate for electrode for electrolysis, adigimatic thickness gauge (manufactured by Mitutoyo Corporation, minimumscale 0.001 mm) was used to calculate an average value of 10 pointsobtained by measuring evenly in the plane. The value was used as thethickness of the substrate for electrode for electrolysis (gaugethickness). For the thickness of the electrode, a digimatic thicknessgauge was used to calculate an average value of 10 points obtained bymeasuring evenly in the plane, in the same manner as for the substratefor electrode. The value was used as the thickness of the electrode(gauge thickness). The thickness of the catalytic layer was determinedby subtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode.

(12) Elastic Deformation Test of Electrode

The ion exchange membrane A (membrane) and the electrode produced in[Method (i)] were each cut into a 110 mm square. The ion exchangemembrane was immersed in pure water for 12 hours or more and then usedfor the test. After the ion exchange membrane and the electrode werelaminated to produce a laminate under conditions of a temperature: 23±2°C. and a relative humidity: 30±5%, the laminate was wound around a PVCpipe having an outer diameter of ϕ32 mm and a length of 20 cm withoutany gap, as shown in FIG. 14. The laminate was fixed using apolyethylene cable tie such that the laminate wound did not come offfrom the PVC pipe or loosen. The laminate was retained in this state for6 hours. Thereafter, the cable tie was removed, and the laminate wasunwound from the PVC pipe. Only the electrode was placed on a surfaceplate, and the heights L₁ and L₂ of a portion lifted from the surfaceplate were measured to determine an average value. This value was usedas the index of the electrode deformation. That is, a smaller valuemeans that the laminate is unlikely to deform.

When an expanded metal is used, there are two winding direction: the SWdirection and the LW direction. In this test, the laminate was wound inthe SW direction.

Deformed electrodes (electrodes that did not return to their originalflat state) were evaluated for softness after plastic deformation inaccordance with a method as shown in FIG. 15. That is, a deformedelectrode was placed on a membrane sufficiently immersed in pure water.One end of the electrode was fixed, and the other lifted end was pressedonto the membrane to release a force, and an evaluation was performedwhether the deformed electrode conformed to the membrane.

(13) Membrane Damage Evaluation

As the membrane, an ion exchange membrane B below was used.

As reinforcement core materials, those obtained by twisting 100 deniertape yarns of polytetrafluoroethylene (PTFE) 900 times/m into a threadform were used. (hereinafter referred to as PTFE yarns). As warpsacrifice yarns, yarns obtained by twisting eight 35 denier filaments ofpolyethylene terephthalate (PET) 200 times/m were used (hereinafterreferred to as PET yarns). As weft sacrifice yarns, yarns obtained bytwisting eight 35 denier filaments of polyethylene terephthalate (PET)200 times/m were used. First, the PTFE yarns and the sacrifice yarnswere plain-woven with 24 PTFE yarns/inch so that two sacrifice yarnswere arranged between adjacent PTFE yarns, to obtain a woven fabrichaving a thickness of 100 μm.

Next, a polymer (A1) of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.92mg equivalent/g and a polymer (B1) of a dry resin that was a copolymerof CF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g were provided. Using these polymers(A1) and (B1), a two-layer film X in which the thickness of a polymer(A1) layer was 25 μm and the thickness of a polymer (E1) layer was 89 μmwas obtained by a coextrusion T die method. As the ion exchange capacityof each polymer, shown was the ion exchange capacity in the case ofhydrolyzing the ion exchange group precursors of each polymer forconversion into ion exchange groups.

Separately, a polymer (B2) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g was provided. This polymer wassingle-layer extruded to obtain a film Y having a thickness of 20 μm.

Subsequently, release paper, the film Y, a reinforcing material, and thefilm X were laminated in this order on a hot plate having a heat sourceand a vacuum source inside and having micropores on its surface, heatedand depressurized under the conditions of a hot plate temperature of225° C. and a degree of reduced pressure of 0.022 MPa for two minutes,and then the release paper was removed to obtain a composite membrane.The resulting composite membrane was immersed in an aqueous solutioncomprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) foran hour for saponification. Thereafter, the membrane was immersed in0.5N NaOH for an hour to replace the ions attached to the ion exchangegroups by Na, and then washed with water. Further, the membrane wasdried at 60° C.

Additionally, a polymer (B3) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.05 mg equivalent/g were hydrolyzed and then was turnedinto an acid type with hydrochloric acid. Zirconium oxide particleshaving an average particle size of primary particles of 0.02 μm wereadded to a 50/50 (mass ratio) mixed solution of water and ethanol inwhich the polymer (B3′) of this acid type was dissolved in a proportionof 5% by mass such that the mass ratio of the polymer (B3′) to thezirconium oxide particles was 20/80. Thereafter, the polymer (B3′) wasdispersed in a suspension of the zirconium oxide particles with a ballmill to obtain a suspension.

This suspension was applied by a spray method onto both the surfaces ofthe ion exchange membrane and dried to obtain an ion exchange membrane Bhaving a coating layer containing the polymer (B3′) and the zirconiumoxide particles. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.35 mg/cm².

The anode used was the same as in (9) Electrolytic evaluation.

The cathode used was one described in each of Examples and ComparativeExamples. The collector, mattress, and feed conductor of the cathodechamber used were the same as in (9) Electrolytic evaluation. That is, azero-gap structure had been provided by use of Ni mesh as the feedconductor and the repulsive force of the mattress as the metal elasticbody. The gaskets used were the same as in (9) Electrolytic evaluation.As the membrane, the ion exchange membrane B produced by the methodmentioned above was used. That is, an electrolyzer equivalent to that in(9) was provided except that the laminate of the on exchange membrane Band the electrode for electrolysis was sandwiched between a pair ofgaskets.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted such that the temperature in each electrolytic cell reached 70°C. Common salt electrolysis was performed at a current density of 8kA/m². The electrolysis was stopped 12 hours after the start of theelectrolysis, and the ion exchange membrane B was removed and observedfor its damage condition.

“0” means no damage. “1 to 3” means that damage was present, and alarger number means a larger degree of damage.

(14) Ventilation Resistance of Electrode

The ventilation resistance of the electrode was measured using an airpermeability tester KES-F8 (trade name, KATO TECH CO., LTD.). The unitfor the ventilation resistance value is kPa·s/m. The measurement wasrepeated 5 times, and the average value was listed in Table 2. Themeasurement was conducted under the following two conditions. Thetemperature of the measuring chamber was 24° C. and the relativehumidity was

Measurement Condition 1 (Ventilation Resistance 1)

Piston speed: 0.2 cm/s

Ventilation volume: 0.4 cc/cm²/s

Measurement range: SENSE L (low)

Sample size: 50 mm×50 mm

Measurement Condition 2 (Ventilation Resistance 2)

Piston speed: 2 cm/s

Ventilation volume: 4 cc/cm²/s

Measurement range: SENSE M (medium) or H (high)

Sample size: 50 mm×50 mm

Example 1

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 16 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.71 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching. The opening ratio was 49%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced in Example 1 was 24μm. The thickness of the catalytic layer, which was determined bysubtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode, was 8 μm. The coatingwas formed also on the surface not roughened. The thickness was thetotal thickness of ruthenium oxide and cerium oxide.

The measurement results of the adhesive force of the electrode producedby the above method are shown in Table 2. A sufficient adhesive forcewas observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The roughenedsurface of the electrode was oppositely disposed on a substantial centerposition of the carboxylic acid layer side of the ion exchange membraneA (size: 160 mm×160 mm), produced in [Method (i)] and equilibrated witha 0.1 N NaOH aqueous solution, and allowed to adhere thereto via thesurface tension of the aqueous solution.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The above membrane-integrated electrode was sandwiched between the anodecell and the cathode cell such that the surface onto which the electrodewas attached was allowed to face the cathode chamber side. In thesectional structure, the collector, the mattress, the nickel mesh feedconductor, the electrode, the membrane, and the anode are arranged inthe order mentioned from the cathode chamber side to form a zero-gapstructure.

The resulting electrode was subjected to electrolytic evaluation. Theresults are shown in Table 2.

The electrode exhibited a low voltage, high current efficiency, and alow common salt concentration in caustic soda. The handling property wasalso good: “1”. The membrane damage was also evaluated as good: “0”.

When the amount of coating after the electrolysis was measured byfluorescent X-ray analysis (XRF), substantially 100% of the coatingremained on the roughened surface, and the coating on the surface notroughened was reduced. This indicates that the surface opposed to themembrane (roughened surface) contributes to the electrolysis and theother surface not opposed to the membrane can achieve satisfactoryelectrolytic performance when the amount of coating is small or nocoating is present.

Example 2

In Example 2, an electrolytic nickel foil having a gauge thickness of 22μm was used as the substrate for electrode for cathode electrolysis. Onesurface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 0.96 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 1, and theresults are shown in Table 2.

The thickness of the electrode was 29 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 7 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0033 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRE,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 3

In Example 3, an electrolytic nickel foil having a gauge thickness of 30μm was used as the substrate for electrode for cathode electrolysis. Onesurface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 1.38 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 1, and theresults are shown in Table 2.

The thickness of the electrode was 38 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating present.

Example 4

In Example 4, an electrolytic nickel foil having a gauge thickness of 16μm was used as the substrate for electrode for cathode electrolysis. Onesurface of this nickel foil was subjected to a roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 0.71 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 75%. Except for the above described,evaluation was performed in the same manner as in Example 1, and theresults are shown in Table 2.

The thickness of the electrode was 24 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 5

In Example 5, an electrolytic nickel foil having a gauge thickness of 20μm was provided as the substrate for electrode for cathode electrolysis.Both the surface of this nickel foil was subjected to a rougheningtreatment by means of electrolytic nickel plating. The arithmeticaverage roughness Ra of the roughened surface was 0.96 μm. Both thesurfaces had the same roughness. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 49%. Except for the above described,evaluation was performed in the same manner as in Example 1, and theresults are shown in Table 2.

The thickness of the electrode was 30 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Additionally, when the amount of coating after the electrolysis wasmeasured by XRF, substantially 100% of the coating remained on both thesurfaces. In consideration of comparison with Examples 1 to 4, thisindicates that the other surface not opposed to the membrane can achievesatisfactory electrolytic performance when the amount of coating issmall or no coating is present.

Example 6

In Example 6, evaluation was performed in the same manner as in Example1 except that coating of the substrate for electrode for cathodeelectrolysis was performed by ion plating, and the results are shown inTable 2. In the ion plating, film forming was performed using Ru metaltarget at the heating temperature of 200° C. and under an argon/oxygenatmosphere at a film forming pressure of 7×10⁻² Pa. The coating formedwas ruthenium oxide.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPA·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 7

In Example 7, the substrate for electrode for cathode electrolysis wasproduced by an electroforming method. The photomask had a shape formedby vertically and horizontally arranging 0.485 mm×0.485 mm squares at aninterval of 0.15 mm. Exposure, development, and electroplating weresequentially performed to obtain a nickel porous foil having a gaugethickness of 20 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.71 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 37 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 17 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 8

In Example 8, the substrate for electrode for cathode electrolysis wasproduced by an electroforming method. The substrate had a gaugethickness of 50 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.73 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 60 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 9

In Example 9, a nickel nonwoven fabric having a gauge thickness of 150μm and a void ratio of 76% (manufactured by NIKKO TECHNO, Ltd.) was usedas the substrate for electrode for cathode electrolysis. The nonwovenfabric had a nickel fiber diameter of about 40 μm and a basis weight of300 g/m². Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 165 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 29 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0612 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 10

In Example 10, a nickel nonwoven fabric having a gauge thickness of 200μm and a void ratio of 72% (manufactured by NIKKO TECHNO, Ltd.) was usedas the substrate for electrode for cathode electrolysis. The nonwovenfabric had a nickel fiber diameter of about 40 μm and a basis weight of500 g/m². Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 215 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 40 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electro had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0164 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 11

In Example 11, foamed nickel having a gauge thickness of 200 μm and avoid ratio of 72% (manufactured by Mitsubishi Materials Corporation) wasused as the substrate for electrode for cathode electrolysis. Except forthe above described, evaluation was performed in the same manner as inExample 1, and the results are shown in Table 2.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 17 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0402 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 12

In Example 12, a 200-mesh nickel mesh having a line diameter of 50 82 m,a gauge thickness of 100 μm, and an opening ratio of 37% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didnot change the opening ratio. It is difficult to measure the roughnessof the surface of the wire mesh. Thus, in Example 12, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness or the wire mesh. Thearithmetic average roughness Ra of a wire piece of the wire mesh was0.64 μm. The measurement of the surface roughness was performed underthe same conditions as for the surface roughness measurement of thenickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example 1,and the results are shown in Table 2.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0154 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage wasevaluated as good: “0”.

Example 13

In Example 13, a 150-mesh nickel mesh having a line diameter of 65 μm, agauge thickness of 130 μm, and an opening ratio of 38% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didnot change the opening ratio. It is difficult to measure the roughnessof the surface of the wire mesh. Thus, in Example 13, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.66 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 1, and the results are shownin Table 2.

The thickness of the electrode was 133 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 3 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 6.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0124 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was also evaluatedas good: “0”.

Example 14

In Example 14, a substrate identical to that of Example 3 (gaugethickness of 30 μm and opening ratio or 44%) was used as the substratefor electrode for cathode electrolysis. Electrolytic evaluation asperformed with a structure identical to that of Example 1 except that nonickel mesh feed conductor was included. That is, in the sectionalstructure of the cell, the collector, the mattress, themembrane-integrated electrode, and the anode are arranged in the ordermentioned from the cathode chamber side to form a zero-gap structure,and the mattress serves as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example 1,and the results are shown in Table 2.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 15

In Example 15, a substrate identical to that of Example 3 (gaugethickness of 30 μm and opening ratio of 44%) was used as the substratefor electrode for cathode electrolysis. The cathode used in ReferenceExample 1, which was degraded and had an enhanced electrolytic voltage,was placed instead of the nickel mesh feed conductor. Except for theabove described, electrolytic evaluation was performed with a structureidentical to that of Example 1. That is, in the sectional structure ofthe cell, the collector, the mattress, the cathode that was degraded andhad an enhanced electrolytic voltage (serves as the feed conductor), theelectrode for electrolysis (cathode), the membrane, and the anode arearranged in the order mentioned from the cathode chamber side to form azero-gap structure, and the cathode that is degraded and has an enhancedelectrolytic voltage serves as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example 1,and the results are shown in Table 2.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 16

A titanium foil having a gauge thickness of 20 μm was provided as thesubstrate for electrode for anode electrolysis. Both the surfaces of thetitanium foil were subjected to a roughening treatment. A porous foilwas formed by perforating this titanium foil with circular holes bypunching. The hole diameter was 1 mm, and the opening ratio was 14%. Thearithmetic average roughness Ra of the surface was 0.37 μm. Themeasurement of the surface roughness was performed under the sameconditions as for the surface roughness measurement of the nickel platesubjected to the blast treatment.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing, the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a chloride (PVC) cylinder was always in contactwith the coating liquid. A coating roll around which the same EPOM hadbeen wound was placed at the upper portion thereof, and PVC roller wasfurther placed thereabove. The coating liquid was applied by allowingthe substrate for electrode to pass between the second coating roll andthe PVC roller at the uppermost portion (roll coating method). After theabove coating liquid was applied onto the titanium porous foil, dryingat 60° C. for 10 minutes and baking at 475° C. for 10 minutes wereperformed. A series of these coating, drying, preliminary baking, andbaking operations was repeatedly performed, and then baking at 520° C.was performed for an hour.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The cutelectrode was allowed to adhere via the surface tension of the aqueoussolution to a substantial center position of the sulfonic acid layerside of the ion exchange membrane A (size: 160 mm×160 mm) produced in[Method (i)] and equilibrated with a 0.1 N NaOH aqueous solution.

The cathode was prepared in the following procedure. First, a 40-meshnickel wire mesh having a line diameter of 150 μm was provided as thesubstrate. After blasted with alumina as pretreatment, the wire mesh wasimmersed in 6 N hydrochloric acid for 5 minutes, sufficiently washedwith pure water, and dried.

Next, a ruthenium chloride solution having a ruthenium concentration of100 g/L (Tanaka Kiknzoku Kogyo K.K.) and cerium chloride (KISHIDACHEMICAL Co., Ltd.) were mixed such that the molar ratio between theruthenium element and the cerium element was 1:0.25. This mixed solutionwas sufficiently stirred and used as a cathode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at. 300°C. for 3 minutes, and baking at 550° C. for 10 minutes were performed.Thereafter, baking at 550° C. for an hour was performed. A series ofthese coating, drying, preliminary baking, and baking operations wasrepeated.

As the collector of the cathode chamber, a nickel expanded metal wasused. The collector had a size of 95 mm in length×110 mm in width. As ametal elastic body, a mattress formed by knitting nickel fine wire wasused. The mattress as the metal elastic body was placed on thecollector. The cathode produced by the above method was placedthereover, and a string made of Teflon (R) was used to fix the fourcorners of the mesh to the collector.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the anodes, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The anode used in Reference Example 3, which was degraded and had anenhanced electrolytic voltage, was fixed to the anode cell by welding,and the above membrane-integrated electrode was sandwiched between theanode cell and the cathode cell such that the surface onto which theelectrode was attached was allowed to face the anode chamber side. Thatis, in the sectional structure of the cell, the collector, the mattress,the cathode, the membrane, the electrode for electrolysis (titaniumporous foil anode), and the anode that was degraded and had an enhancedelectrolytic voltage were arranged in the order mentioned from thecathode chamber side to form a zero-gap structure. The anode that wasdegraded and had an enhanced electrolytic voltage served as the feedconductor. The titanium porous foil anode and the anode that wasdegraded and had an enhanced electrolytic voltage were only in physicalcontact with each other and were not fixed with each other by welding.

Evaluation on this structure was performed in the same manner as inExample 1, and the results are shown in Table 2.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 6 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 4 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and, 0.0060 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 17

In Example 17, a titanium foil having a gauge thickness of 20 μm and anopening ratio of 30% was used as the substrate for electrode for anodeelectrolysis. The arithmetic average roughness Ra of the surface was0.37 μm. The measurement of the surface roughness was performed underthe same conditions as for the surface roughness measurement of thenickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example 16,and the results are shown in Table 2.

The thickness of the electrode was 30 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 5 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 18

In Example 18, a titanium foil having a gauge thickness of 20 μm and anopening ratio of 42% was used as the substrate for electrode for anodeelectrolysis. The arithmetic average roughness Ra of the surface was0.38 μm. The measurement of the surface roughness was performed underthe same conditions as for the surface roughness measurement of thenickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example 16,and the results are shown in Table 2.

The thickness of the electrode was 32 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 12 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0022 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 19

In Example 19, a titanium foil having a gauge thickness of 50 μm and anopening ratio of 47% was used as the substrate for electrode for anodeelectrolysis. The arithmetic average roughness Ra of the surface was0.40 μm. The measurement of the surface roughness was performed underthe same conditions as for the surface roughness measurement of thenickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example 16,and the results are shown in Table 2.

The thickness of the electrode was 69 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 19 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 8 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0024 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 20

In Example 20, a titanium nonwoven fabric having a gauge thickness of100 μm, a titanium fiber diameter of about 20 μm, a basis weight of 100g/m², and an opening ratio of 78% was used as the substrate forelectrode for anode electrolysis. Except for the above described,evaluation was performed in the same manner as in Example 16, and theresults are shown in Table 2.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0228 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 21

In Example 21, a 150-mesh titanium wire mesh having a gauge thickness of120 μm and a titanium fiber diameter of about 60 μm was used as thesubstrate for electrode for anode electrolysis. The opening ratio was42%. A blast treatment was performed with alumina of grain-size number320. It is difficult to measure the roughness of the surface of the wiremesh. Thus, in Example 21, a titanium plate having a thickness of 1 mmwas simultaneously subjected to the blast treatment during the blasting,and the surface roughness of the titanium plate was taken as the surfaceroughness of the wire mesh. The arithmetic average roughness Ra was 0.60μm. The measurement of the surface roughness was performed under thesame conditions as for the surface roughness measurement of the nickelplate subjected to the blast treatment. Except for the above described,evaluation was performed in the same manner as Example 16, and theresults are shown in Table 2.

The thickness of the electrode was 140 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 20 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 10 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0132 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 22

In Example 22, an anode that was degraded and had an enhancedelectrolytic voltage was used in the same manner as in Example 16 as theanode feed conductor, and a titanium nonwoven fabric to that of Example20 was used as the anode. A cathode that was degraded and had anenhanced electrolytic voltage was used in the same manner as in Example15 as the cathode feed conductor, and a nickel foil electrode identicalto that of Example 3 was used as the cathode. In the sectional structureof the cell, the collector, the mattress, the cathode that was degradedand had an enhanced voltage, the nickel porous foil cathode, themembrane, the titanium nonwoven fabric anode, and the anode that wasdegraded and had an enhanced electrolytic voltage are arranged in theorder mentioned from the cathode chamber side to form a zero-gapstructure, and the cathode and anode degraded and having an enhancedelectrolytic voltage serve as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example 1,and the results are shown in Table 2.

The thickness of the electrode (anode) was 114 μm, and the thickness ofthe catalytic layer, which was determined by subtracting the thicknessof the substrate for electrode for electrolysis from the thickness orthe electrode (anode), was 14 μm. The thickness of the electrode(cathode) was 38 μm, and the thickness of the catalytic layer, which wasdetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode (cathode), was 8μm.

A sufficient adhesive force was observed both in the anode and thecathode.

When a deformation test of the electrode (anode) was performed, theaverage value of L₁ and L₂ was 2 mm. When a deformation test of theelectrode (cathode) was performed, the average value of L₁ and L₂ was 0mm.

When the ventilation resistance of the electrode (anode) was measured,the ventilation resistance was 0.07 (kPa·s/m) or less under themeasurement condition 1 and 0.0228 (kPa·s/m) under the measurementcondition 2. When the ventilation resistance of the electrode (cathode)was measured, the ventilation resistance was 0.07 (kPa·s/m) or lessunder the measurement condition 1 and 0.0027 (kPa·s/m) under themeasurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0” both in the anode and the cathode. In Example 22,the cathode and the anodes were combined by attaching the cathode to onesurface of the membrane and the anode to the other surface and subjectedto the membrane damage evaluation.

Example 23

In Example 23, a microporous membrane “Zirfon Perl UTP 500” manufacturedby Agfa was used.

The Zirfon membrane was immersed in pure water for 12 hours or more andused for the test. Except for the above described, the above evaluationwas performed in the same manner as in Example 3, and the results areshown in Table 2.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

Similarly to the case where an ion exchange membrane was used as themembrane, a sufficient adhesive force was observed. The microporousmembrane was brought into a close contact with the electrode via thesurface tension, and the handling property was good: “1”.

Example 24

A carbon cloth obtained by weaving a carbon fiber having a gaugethickness of 566 μm was provided as the substrate for electrode forcathode electrolysis. A coating liquid for use in forming an electrodecatalyst on this carbon cloth was prepared by the following procedure. Aruthenium nitrate solution having a ruthenium concentration of 100 g/L(FURUYA METAL Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.)were mixed such that the molar ratio between the ruthenium element andthe cerium element was 1:0.25. This mixed solution was sufficientlystirred and used as a cathode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088 (tradename), thickness 10 mm)) around a polyvinyl chloride (PVC) cylinder wasalways in contact with the above coating liquid. A coating roll aroundwhich the same EPDM had been wound was placed at the upper portionthereof, and a PVC roller was further placed thereabove. The coatingliquid was applied by allowing the substrate for electrode to passbetween the second coating roll and the PVC roller at the uppermostportion (roll coating method). Then, after drying at 50° C. for 10minutes, preliminary baking at 150° C. for 3 minutes, and baking at 350°C. for 10 minutes were performed. A series of these coating, drying,preliminary baking, and baking operations was repeated until apredetermined amount of coating was achieved. The thickness of theelectrode produced was 570 μm. The thickness of the catalytic layer,which was determined by subtracting the thickness of the substrate forelectrode for electrolysis from the thickness of the electrode, was 4μm. The thickness of the catalytic layer was the total thickness ofruthenium oxide and cerium oxide.

The resulting electrode was subjected to electrolytic evaluation. Theresults are shown in Table 2.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.19 (kPa·s/m) under the measurementcondition 1 and 0.176 (kPa·s/m) under the measurement condition 2.

The electrode had a handling property of “2” and was determined to behandleable as a large laminate.

The voltage was high, the membrane damage was evaluated as “1”, andmembrane damage was observed. It was conceived that this is because NaOHthat had been generated in the electrode accumulated on the interfacebetween the electrode and the membrane to elevate the concentrationthereof, due to the high ventilation resistance of the electrode ofExample 24.

Reference Example 1

In Reference Example 1, used was a cathode used as the cathode in alarge electrolyzer for eight years, degraded, and having an enhancedelectrolytic voltage. The above cathode was placed instead of the nickelmesh feed conductor on the mattress of the cathode chamber, and the ionexchange membrane A produced in [Method (i)] was sandwichedtherebetween. Then, electrolytic evaluation was performed. In ReferenceExample 1, no membrane-integrated electrode was used. In the sectionalstructure of the cell, the collector, the mattress, the cathode that wasdegraded and had an enhanced electrolytic voltage, the ion exchangemembrane A, and the anodes were arranged in the order mentioned from thecathode chamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.04 V, the current efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was20 ppm. Consequently, due to degradation of the cathode, the voltage washigh.

Reference Example 2

In Reference Example 2, a nickel mesh feed conductor was used as thecathode. That is, electrolysis was performed on nickel mesh having nocatalyst coating thereon.

The nickel mesh cathode was placed on the mattress of the cathodechamber, and the ion exchange membrane A produced in [Method (i)] wassandwiched therebetween. Then, electrolytic evaluation was performed. Inthe sectional structure of the electric cell of Reference Example 2, thecollector, the mattress, the nickel mesh, the ion exchange membrane A,and the anodes were arranged in the order mentioned from the cathodechamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.38 V, the current efficiency was 97.7%, the common saltconcentration in caustic soda (value converted on the basis of 50%) wasppm. Consequently, the voltage was nigh because the cathode catalyst hadno coating.

Reference Example 3

In Reference Example 3, used was an anode used as the anode in a largeelectrolyzer for about eight years, degraded, and having an enhancedelectrolytic voltage.

In the sectional structure of the electrolytic cell of Reference Example3, the collector, the mattress, the cathode, the ion exchange membrane Aproduced in [Method (i)], and the anode that was degraded and had anenhanced electrolytic voltage were arranged in the order mentioned fromthe cathode chamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.18 V, the current efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was22 ppm. Consequently, due to degredation of the anode, the voltage washigh.

Comparative Example 1

In Comparative Example 1, a fully-rolled nickel expanded metal having agauge thickness of 100 μm and an opening ratio of 33% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 1,a nickel plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe nickel plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.68 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

The mass per unit area was 67.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.05 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was 64%, and the result of evaluation of winding around column of 145 mmin diameter (3) was 22%. The portions at which the electrode came offfrom the membrane increased. This is because there were problems in thatthe electrode was likely to come off when the membrane-integratedelectrode was handled and in that the electrode came off and fell fromthe membrane during handled. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Comparative Example 2

In Comparative Example 2, a fully-rolled nickel expanded metal having agauge thickness of 100 μm and an opening ratio of 16% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 2,a nickel plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe nickel plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.64 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 107 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm.

The mass per unit area was 78.1 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.04 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was 37%, and the result of evaluation of winding around column of 145 mmin diameter (3) was 25%. The portions at which the electrode came offfrom the membrane increased. This is because there were problems in thatthe electrode was likely to come off when the membrane-integratedelectrode was handled and in that the electrode came off and fell fromthe membrane during handled. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 18.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0176 (kPa·s/m) under the measurement condition 2.

Comparative Example 3

In Comparative Example 3, a fully-rolled nickel expanded metal having agauge thickness of 100 μm and an opening ratio of 40% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 3,a nickel plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe nickel plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.70 μm. The measurement of thesurface roughness m performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment.

Coating of the substrate for electrode for electrolysis was performed byion plating in the same manner as in Example 6. Except for the abovedescribed, evaluation was performed in the same manner as in Example 1,and the results are shown in Table 2.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

The force applied per unit mass·unit area (1) was such a small value as0.07 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter (2) was 80%, and the result of evaluation ofwinding around column of 145 mm in diameter (3) was 32%. The portions atwhich the electrode came off from the membrane increased. This isbecause there were problems in that the electrode was likely to come offwhen the membrane-integrated electrode was handled and in that theelectrode came off and fell from the membrane during handled. Thehandling property was “3”, which was also problematic. The membranedamage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Comparative Example 4

In Comparative Example 4, a fully-rolled nickel expanded metal having agauge thickness of 100 μm and an opening ratio of 58% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 4,a nickel plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe nickel plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.64 μm. The measurement Of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 109 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 9 μm.

The force applied per unit mass·unit area (1) was such a small value as0.06 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter (2) was 69%, and the result of evaluation ofwinding around column of 145 mm in diameter (3) was 39%. The portions atwhich the electrode came off from the membrane increased. This isbecause there were problems in that the electrode was likely to come offwhen the membrane-integrated electrode was handled and in that theelectrode came off and fell from the membrane during handled. Thehandling property was “3”, which was also problematic. The membranedamage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

Comparative Example 5

In Comparative Example 5, a nickel wire mesh having gauge thickness of300 μm and an opening ratio of 56% was used as the substrate forelectrode for cathode electrolysis. It is difficult to measure thesurface roughness of the wire mesh. Thus, in Comparative Example 5, anickel plate having a thickness of 1 mm was simultaneously subjected tothe last treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire A blasttreatment was performed with alumina of grain-size number 320. Theopening ratio was not changed after the blast treatment. The arithmeticaverage roughness Ra was 0.64 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 1, and the results are shown in Table 2.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 49.2 (mg/cm²). Thus, the result of evaluationof winding around column of 280 mm in diameter was 88%, and the resultof evaluation of winding around column of 145 mm in diameter (3) was42%. The portions at which the electrode came off from the membraneincreased. This is because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehandling property, which was evaluated as “3”. When the large sizeelectrode was actually operated, it was possible to evaluate thehandling property as “3”. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

Comparative Example 6

In Comparative Example 6, a nickel wire mesh having a gauge thickness of200 μm and an opening ratio of 37% was used as the substrate forelectrode for cathode electrolysis. A blast treatment was performed withalumina of grain-size number 320. The opening ratio was not changedafter the blast treatment. It is difficult to measure the surfaceroughness of the wire mesh. Thus, in Comparative Example 6, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.65 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation of electrodeelectrolysis, measurement results of the adhesive force, andadhesiveness were performed in the same manner as in Example 1. Theresults are shown in Table 2.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

The mass per unit area was 56.4 mg/cm². Thus, the result of evaluationmethod of winding around column of 145 mm in diameter (3) was 63%, andthe adhesiveness between the electrode and the membrane was poor. Thisis because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehandling property, which was evaluated as “3”. The membrane damage wasevaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 19 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0096 (kPa·s/m) under the measurement condition 2.

Comparative Example 7

In Comparative Example 7, a full-rolled titanium expanded metal having agauge thickness of 500 μm and an opening ratio of 17% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 7,a titanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.60 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 16, and the results are shown in Table 2.

The thickness of the electrode was 508 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 152.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition and 0.0072 (kPa·s/m) under the measurement condition 2.

Comparative Example 8

In Comparative Example 8, a full-rolled titanium expanded metal having agauge thickness of 800 μm and an opening ratio of 8% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 8,a titanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.61 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 16, and the results are shownin Table 2.

The thickness of the electrode was 808 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 251.3 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0172 (kPa·s/m) under the measurement condition 2.

Comparative Example 9

In Comparative Example 9, a full-rolled titanium expanded metal having agauge thickness of 1000 μm and an opening ratio of 46% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Comparative Example 9,a titanium plate having, a thickness of 1 mm was simultaneouslysubjected to the blast treatment during the blasting, and the surfaceroughness of the titanium plate was taken as the surface roughness ofthe wire mesh. The arithmetic average roughness Ra was 0.59 μm. Themeasurement of the surface roughness was performed under the sameconditions as for the surface roughness measurement of the nickel platesubjected to the blast treatment. Except for the above described, theabove evaluation was performed in the same manner as in Example 16, andthe results are shown in Table 2.

The thickness of the electrode was 1011 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 11 μm.

The mass per unit area was 245.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Comparative Example 10

In Comparative Example 10, a membrane electrode assembly was produced bythermally compressing an electrode onto a membrane with reference to aprior art document (Examples of Japanese Patent Laid-Open No. 58-48686).

A nickel expanded metal having a gauge thickness of 100 μm and anopening ratio or 33% was used as the substrate for electrode for cathodeelectrolysis to perform electrode coating in the same manner as inExample 1. Thereafter, one surface of the electrode was subjected to aninactivation treatment in the following procedure. Polyimide adhesivetape (Chukoh Chemical Industries, Ltd.) was attached to one surface ofthe electrode. A PTFE dispersion (Dupont-Mitsui Cluorochemicals Co.,Ltd., 31-JR (trade name)) was applied onto the other surface and driedin a muffle furnace at 120° C. for 10 minutes. The polyimide tape waspeeled off, and a sintering treatment was performed in a muffle furnaceset at 380° C. for 10 minutes. This operation was repeated twice toinactivate the one surface of the electrode.

Produced was a membrane formed by two layers of a perfluorocarbonpolymer of which terminal functional group is “—COOCH₃” (C polymer) anda perfluorocarbon polymer of which terminal group is “—SO₂F” (Spolymer). The thickness of the C polymer layer was 3 mils, and thethickness of the S polymer layer was 4 mils. This two-layer membrane wassubjected to a saponification treatment to thereby introduce ionexchange groups to the terminals of the polymer by hydrolysis. The Cpolymer terminals were hydrolyzed into carboxylic acid groups and the Spolymer terminals into sulfo groups. The ion exchange capacity as thesulfonic acid group was 1.0 meq/g, and the ion exchange capacity as thecarboxylic acid group was 0.9 meq/g.

The inactivated electrode surface was oppositely disposed to andthermally pressed onto the surface having carboxylic acid groups as theion exchange groups to integrate the ion exchange membrane and theelectrode. The one surface of the electrode was exposed even after thethermal compression, and the electrode passed through no portion of themembrane.

Thereafter, in order to suppress attachment of bubbles to be generatedduring electrolysis to the membrane, a mixture of zirconium oxide and aperfluorocarbon polymer into which sulfo groups had been introduced wasapplied onto both the surfaces. Thus, the membrane electrode assembly ofComparative Example 10 was produced.

When the force applied per unit mass·unit area (1) was measured usingthis membrane electrode assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.50 (N/mg·cm²) was applied, aportion of the membrane was broken. The membrane electrode assembly ofComparative Example 10 had a force applied per unit mass·unit area (1)of at least 1.50 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed, the area in contact with the plastic pipe was less than 5%.Meanwhile, when evaluation of winding around column of 280 mm indiameter (2) was performed, the electrode and the membrane were 100%bonded to each other, but the membrane was not wound around the columnin the first place. The result of evaluation of winding around column of145 mm in diameter (3) was the same. The result meant that theintegrated electrode impaired the handling property of the membrane tothereby make it difficult to roll the membrane into a roll and fold themembrane. The handling property was “3”, which was problematic. Themembrane damage was evaluated as “0”. Additionally, when electrolyticevaluation was performed, the voltage was high, the current efficiencywas low, the common salt concentration in caustic soda (value convertedon the basis of 50%) was raised, and the electrolytic performancedeteriorated.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 14 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Comparative Example 11

In Comparative Example 11, a 40-mesh nickel mesh having a line diameterof 150 μm, a gauge thickness of 300 μm, and an opening ratio of 58% wasused as the substrate for electrode for cathode electrolysis. Except forthe above described, a membrane electrode assembly was produced in thesame manner as in Comparative Example 10.

When the force applied per unit mass·unit area (1) was measured usingthis membrane electrode assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.60 (N/mg·cm²) was applied, aportion of the membrane was broken. The membrane electrode assembly ofComparative Example 11 had a force applied per unit mass·unit area (1)of at least 1.60 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed using this membrane electrode assembly, the contact area withthe plastic pipe was less than 5%. Meanwhile, when evaluation. ofwinding around column of 280 mm in diameter (2) was performed, theelectrode and the membrane were 100% bonded to each other, but themembrane was not wound around the column in the first place. The resultof evaluation of winding around column of 145 mm in diameter (3) was thesame. The result meant that the integrated electrode impaired thehandling property of the membrane to thereby make it difficult to rollthe membrane into a roll and fold the membrane. The handling propertywas “3”, which was problematic. Additionally, when electrolyticevaluation was performed, the voltage was high, the current efficiencywas low, the common salt concentration in caustic soda was raised, andthe electrolytic performance deteriorated.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

Comparative Example 12 (Preparation of Catalyst)

A metal salt aqueous solution was produced by adding 0.728 g of silvernitrate (Wako Pure Chemical Industries, Ltd.) and 1.86 g of ceriumnitrate hexahydrate (Wako Pure Chemical Industries, Ltd.) to 150 ml ofpure water. An alkali solution was produced by adding 240 g of purewater to 100 g of a 15% tetramethylammonium hydroxide aqueous solution(Wako Pure Chemical Industries, Ltd.). While the alkali solution wasstirred using a magnetic stirrer, the metal salt aqueous solution wasadded thereto dropwise at 5 ml/minute using a buret. A suspensioncontaining the resulting metal hydroxide particulates wassuction-filtered and then washed with water to remove the alkalicontent. Thereafter, the residue was transferred into 200 ml of2-propanol (KISHIDA CHEMICAL Co., Ltd.) and redispersed by an ultrasonicdispersing apparatus (US-600T, NISSEI Corporation) for 10 minutes toobtain a uniform suspension.

A suspension of carbon black was obtained by dispersing 0.36 g ofhydrophobic carbon black (DENKA BLACK(R) AB-7 (trade name), DenkaCompany Limited) and 0.84 g of hydrophilic carbon black (Ketjenblack(R)EC-600JD (trade name), Mitsubishi Chemical Corporation) in 100 ml of2-propanol and dispersing the mixture by the ultrasonic dispersingapparatus for 10 minutes. The metal hydroxide precursor suspension andthe carbon black suspension were mixed and dispersed by the ultrasonicdispersing apparatus for 10 minutes. This suspension wassuction-filtered and dried at room temperature for half a day to obtaincarbon black containing the metal hydroxide precursor dispersed andfixed. Subsequently, an inert gas baking furnace (VMF165 type, YAMADADENKI CO., LTD.) was used to perform baking in a nitrogen atmosphere at400° C. for an hour to obtain carbon black A containing an electrodecatalyst dispersed and fixed.

(Production of Powder for Reaction Layer)

To 1.6 g of the carbon black A containing an electrode catalystdispersed and fixed, 0.84 ml of a surfactant Triton(R) X-100(trade name,ICN Biomedicals) diluted to 20% by weight with pure water and 15 ml ofpure water, and the mixture was dispersed by an ultrasonic dispersingapparatus for 10 minutes. To this dispersion, 0.664 g of apolytetrafluoroethylene (PTFE) dispersion (PTFE30J (trade name),Dupont-Mitsui Fluorochemicals Co., Ltd.) was added. After the mixturewas stirred for five minutes, suction filtration was performed.Additionally, the residue was dried in a dryer at 80° C. for an hour,and pulverization was performed by a mill to obtain a powder forreaction layer A.

(Production of Powder for Gas Diffusion Layer)

Dispersed were 20 g of hydrophobic carbon black (DENKA BLACK(R) AB-7(trade name)), 50 ml of a surfactant Triton(R) X-100 (trade name)diluted to 20% by weight with pure water, and 360 ml of pure, water byan ultrasonic dispersing apparatus for 10 minutes. To the resultingdispersion, 22.32 g of the PTFE dispersion was added. The mixture wasstirred for 5 minutes, and then, filtration was performed. Additionally,the residue was dried in a dryer at 80° C. for an hour, andpulverization was performed by a mill to obtain a powder for gasdiffusion layer A.

(Production of Gas Diffusion Electrode)

To 4 g of the powder for gas diffusion layer A, 8.7 ml of ethanol wasadded, and the mixture was kneaded into a paste form. This powder forgas diffusion layer in a paste form was formed into a sheet form by aroll former. Silver mesh (SW=1, LW=2, and thickness=0.3 mm) as thecollector was embedded into the sheet and finally formed into a sheetform having a thickness of 1.8 mm. To 1 g of the powder for reactionlayer A, 2.2 ml of ethanol was added, and the mixture was kneaded into apaste form. This powder for reaction layer in a paste form was formedinto a sheet form having a thickness of 0.2 mm. Additionally, the twosheets, that is, the sheet obtained by using the powder for gasdiffusion layer A produced and the sheet obtained by using the powderfor reaction layer A were laminated and formed into a sheet form havinga thickness of 1.8 mm by a roll former. This laminated sheet was driedat room temperature for a whole day and night to remove ethanol.Further, in order to remove the remaining surfactant, the sheet wassubjected to a pyrolysis treatment in air at 300° C. for an hour. Thesheet was wrapped in an aluminum foil, and subjected to hot pressing bya hot pressing machine (SA303 (trade name), TESTER SANGYO CO., LTD.) at360° C. and 50 kgf/cm² for 1 minute to obtain a gas diffusion electrode.The thickness of the gas diffusion electrode was 412 μm.

The resulting electrode was used to perform electrolytic evaluation. Inthe sectional structure of the electrolytic cell, the collector, themattress, the nickel mesh feed conductor, the electrode, the membrane,and the anode are arranged in the order mentioned from the cathodechamber side to form a zero-gap structure. The results are shown inTable 2.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 19 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 25.88 (kPa·s/m) under the measurementcondition 1.

The handling property was “3”, which was problematic. Additionally, whenelectrolytic evaluation was performed, the current efficiency was low,the common salt concentration in caustic soda was raised, and theelectrolytic performance markedly deteriorated. The membrane damage,which was evaluated as “3”, also bad a problem.

These results have revealed that the gas diffusion electrode obtained inComparative Example 12 had markedly poor electrolytic performance.Additionally, damage was observed on the substantially entire surface ofthe ion exchange membrane. It was conceived that this is because NaOHthat had been generated in the electrode accumulated on the interfacebetween the electrode and the membrane to elevate the concentrationthereof, due to the markedly high ventilation resistance of the gasdiffusion electrode of Comparative Example 12.

Comparative Example 13

A nickel line having a gauge thickness of 150 μm was provided as thesubstrate for electrode for cathode electrolysis. A roughening treatmentby this line was performed. It is difficult to measure the surfaceroughness of the nickel line. Thus, in Comparative Example 13, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the nickel line. Ablast treatment was performed with alumina of grain-size number 320. Thearithmetic average roughness Ra was 0.64 μm.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088 (tradename), thickness 10 mm) around a polyvinyl chloride (PVC) cylinder wasalways in contact with the above coating liquid. A coating roll aroundwhich the same EPDM had been wound was placed at the upper portionthereof, and a PVC roller was further placed thereabove. The coatingliquid was applied by allowing the substrate for electrode to passbetween the second coating roll and the PVC roller at the uppermostportion (roll coating method). Then, after drying at 50° C. for 10minutes, preliminary baking at 150° C. for 3 minutes, and baking at 350°C. for 10 minutes were performed. A series of these coating, drying,preliminary baking, and baking operations was repeated until apredetermined amount of coating was achieved. The thickness of onenickel line produced in Comparative Example 13 was 158 μm.

The nickel line produced by the above method was cut into a length of110 mm and a length of 95 mm. As shown in FIG. 16, the 110 mm nickelline and the 95 mm nickel line were placed surface that the nickel linesvertically overlapped each other at the center of each of the nickellines and bonded to each other at the intersection with an instantadhesive (Aron Alpha(R), TOAGOSEI CO., LTD.) to produce an electrode.The electrode was evaluated, and the results are shown in Table 2.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.7%.

The mass per unit area of the electrode was 0.5 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 15 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance value was 0.0002(kPa·s/m).

Additionally, the structure shown in FIG. 17 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.16 V.

Comparative Example 14

In Comparative Example 14, the electrode produced in Comparative Example13 was used. As shown in FIG. 18, the 110 mm nickel line and the 95 mmnickel line were placed such that the nickel lines vertically overlappedeach other at the center of each of the nickel lines and bonded to eachother at the intersection with an instant adhesive (Aron Alpha(R),TOAGOSEI CO., LTD.) to produce an electrode. The electrode wasevaluated, and the results are shown in Table 2.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.4%.

The mass per unit area of the electrode was 0.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 16 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0004 (kPa·s/m).

Additionally, the structure shown in FIG. 19 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

Comparative Example 15

In Comparative Example 15, the electrode produced in Comparative Example13 was used. As shown in FIG. 20, the 110 mm nickel line and the 95 mmnickel line were placed such that the nickel lines vertically overlappedeach other at the center of each of the nickel lines and bonded to eachother at the intersection with an instant adhesive (Aron Alpha(R),TOAGOSEI CO., LTD.) to produce an electrode. The electrode wasevaluated, and the results are shown in Table 2.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was98.8%.

The mass per unit area of the electrode was 1.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 14 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0005 (kPa·s/m).

Additionally, the structure shown in FIG. 21 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

TABLE 1 Substrate for Form of substrate Coating electrode for electrodemethod Feed conductor Example 1 Ni Punching Pyrolysis Ni mesh Example 2Ni Punching Pyrolysis Ni mesh Example 3 Ni Punching Pyrolysis Ni meshExample 4 Ni Punching Pyrolysis Ni mesh Example 5 Ni Punching PyrolysisNi mesh Example 6 Ni Punching Ion plating Ni mesh Example 7 NiElectroforming Pyrolysis Ni mesh Example 8 Ni Electroforming PyrolysisNi mesh Example 9 Ni Nonwoven fabric Pyrolysis Ni mesh Example 10 NiNonwoven fabric Pyrolysis Ni mesh Example 11 Ni Foamed Ni Pyrolysis Nimesh Example 12 Ni Mesh Pyrolysis Ni mesh Example 13 Ni Mesh PyrolysisNi mesh Example 14 Ni Punching (same Pyrolysis Mattress as in Example 3)Example 15 Ni Punching (same Pyrolysis Cathode having increase involtage as in Example 3) Example 16 Ti Punching Pyrolysis Anode havingincrease in voltage Example 17 Ti Punching Pyrolysis Anode havingincrease in voltage Example 18 Ti Punching Pyrolysis Anode havingincrease in voltage Example 19 Ti Punching Pyrolysis Anode havingincrease in voltage Example 20 Ti Nonwoven fabric Pyrolysis Anode havingincrease in voltage Example 21 Ti Mesh Pyrolysis Anode having increasein voltage Example 22 Ni/Ti Combination of Pyrolysis Cathode and anodehaving increase in voltage Example 3 and Example 20 Example 23 NiPunching Pyrolysis — Example 24 Carbon Woven fabric Pyrolysis Ni meshComparative Example 1 Ni Expanded Pyrolysis Ni mesh Comparative Example2 Ni Expanded Pyrolysis Ni mesh Comparative Example 3 Ni Expanded Ionplating Ni mesh Comparative Example 4 Ni Expanded Pyrolysis Ni meshComparative Example 5 Ni Mesh Pyrolysis Ni mesh Comparative Example 6 NiMesh Pyrolysis Ni mesh Comparative Example 7 Ti Expanded Pyrolysis Anodehaving increase in voltage Comparative Example 8 Ti Expanded PyrolysisAnode having increase in voltage Comparative Example 9 Ti ExpandedPyrolysis Anode having increase in voltage Comparative Example 10 NiExpanded Pyrolysis Ni mesh Comparative Example 11 Ni Mesh Pyrolysis Nimesh Comparative Example 12 Carbon Powder Pyrolysis Ni mesh ComparativeExample 13 Ni Mesh Pyrolysis Ni mesh Comparative Example 14 Ni MeshPyrolysis Ni mesh Comparative Example 15 Ni Mesh Pyrolysis Ni mesh

TABLE 2 Thickness of substrate for electrode for Thickness of ThicknessMass per Force applied per unit electrolysis electrode of catalyticOpening ratio unit area mass · unit area (1) (μm) (μm) layer (μm) (voidratio) % (mg/cm²) (N/mg · cm²-electrode) Example 1 16 24 8 49 5.8 0.90Example 2 22 29 7 44 9.9 0.61 Example 3 30 38 8 44 11.1 0.43 Example 416 24 8 75 3.5 0.28 Example 5 20 30 10 49 6.4 0.59 Example 6 16 26 10 496.2 0.81 Example 7 20 37 17 56 8.1 0.79 Example 8 50 60 10 56 18.1 0.13Example 9 150 165 15 76 31.9 0.22 Example 10 200 215 15 72 46.3 0.12Example 11 200 210 10 72 36.5 0.13 Example 12 100 110 10 37 27.4 0.18Example 13 130 133 3 38 36.3 0.15 Example 14 30 38 8 44 11.1 0.43Example 15 30 38 8 44 11.1 0.43 Example 16 20 26 6 14 8.9 0.16 Example17 20 30 10 30 8.1 0.26 Example 18 20 32 12 42 6.6 0.24 Example 19 50 6919 47 12.9 0.12 Example 20 100 114 14 78 11.3 0.59 Example 21 120 140 2042 14.9 0.47 Example 22 30/100 38/114 8/14 44/78 11.1/11.3 0.43/0.59Example 23 30 38 8 44 11.1 0.28 Example 24 566 570 4 83 21.8 0.270Comparative Example 1 100 114 14 33 67.5 0.05 Comparative Example 2 100107 7 16 78.1 0.04 Comparative Example 3 100 110 10 40 37.8 0.07Comparative Example 4 100 109 9 58 39.2 0.06 Comparative Example 5 300308 8 56 49.2 0.18 Comparative Example 6 200 210 10 37 56.4 0.09Comparative Example 7 500 508 8 17 152.5 0.01 Comparative Example 8 800808 8 8 251.3 0.01 Comparative Example 9 1000 1011 11 46 245.5 0.01Comparative Example 10 100 114 14 33 67.5 1.50 Comparative Example 11300 308 8 58 49.2 1.80 Comparative Example 12 412 412 — — 101 0.005Comparative Example 13 300 306 6 99.7 0.5 Equal to or less than themeasurement lower limit Comparative Example 14 300 306 6 99.4 0.9 Equalto or less than the measurement lower limit Comparative Example 15 300306 6 98.8 1.9 Equal to or less than the measurement lower limit Methodfor Method for Method for evaluating evaluating evaluating windingwinding winding around around around column of column of column of 280mm in 145 mm in 280 mm in diameter (2) diameter (3) diameter (1)(membrane (membrane Handing Force applied per unit (membrane and andproperty mass · unit area (2) and column) electrode) electrode) (sensory(N/mg · cm²-electrode) (%) (%) (%) evaluation) Example 1 0.640 100 100100 1 Example 2 0.235 100 100 100 1 Example 3 0.194 100 100 100 1Example 4 0.113 100 100 100 1 Example 5 0.386 100 100 100 1 Example 60.650 100 100 100 1 Example 7 0.184 100 100 100 1 Example 8 0.088 100100 100 1 Example 9 0.217 100 100 100 2 Example 10 0.081 100 100 79 2Example 11 0.162 100 100 100 2 Example 12 0.126 100 100 100 1 Example 130.098 100 100 88 2 Example 14 0.194 100 100 100 1 Example 15 0.194 100100 100 1 Example 16 0.105 100 100 100 1 Example 17 0.132 100 100 100 1Example 18 0.147 100 100 100 1 Example 19 0.08 100 100 100 1 Example 200.378 100 100 100 1 Example 21 0.306 100 100 100 1 Example 220.194/0.378 100/100 100/100 100/100 1/1 Example 23 0.194 100 100 100 1Example 24 0.3 100 100 100 2 Comparative Example 1 0.045 100 64 22 4Comparative Example 2 0.027 100 37 25 4 Comparative Example 3 0.045 10080 32 3 Comparative Example 4 0.034 100 69 39 3 Comparative Example 50.138 100 88 42 3 Comparative Example 6 0.060 100 100 63 3 ComparativeExample 7 0.005 100 Less than 5 Less than 5 4 Comparative Example 80.006 100 Less than 5 Less than 5 4 Comparative Example 9 0.005 100 Lessthan 5 Less than 5 4 Comparative Example 10 — Less than 5 — — 3Comparative Example 11 — Less than 5 — — 3 Comparative Example 12 0.005Less than 5 — — 3 Comparative Example 13 Equal to or less than the Lessthan 5 — — 4 measurement lower limit Comparative Example 14 Equal to orless than the Less than 5 — — 4 measurement lower limit ComparativeExample 15 Equal to or less than the Less than 5 — — 4 measurement lowerlimit Elastic deformation test of electrode Electrolytic evaluation(winding around Common salt vinyl chloride Ventilation Ventilationconcentration pipe of 32 mm in resistance resistance Current in causticsoda outer diameter) (KPa · s/m) (KPa · s/m) Membrane Voltage efficiency(ppm, on the average value of (measurement (measurement damage (V) (%)basis of 50%) L₁ and L₂ (mm) condition 1) condition 2) evaluationExample 1 2.98 97.7 15 0 0.07 or less 0.0028 0 Example 2 2.95 97.2 18 00.07 or less 0.0033 0 Example 3 2.96 97.6 19 0 0.07 or less 0.0027 0Example 4 2.97 97.5 15 0 0.07 or less 0.0023 0 Example 5 2.95 97.1 18 00.07 or less 0.0023 0 Example 6 2.96 97.3 14 0 0.07 or less 0.0028 0Example 7 2.96 97.3 15 0 0.07 or less 0.0032 0 Example 8 2.96 97.7 16 00.07 or less 0.0032 0 Example 9 2.97 96.8 23 29 0.07 or less 0.0612 0Example 10 2.96 96.7 26 40 0.07 or less 0.0164 0 Example 11 3.05 97.4 2217 0.07 or less 0.0402 0 Example 12 3.11 97.2 23 0.5 0.07 or less 0.01540 Example 13 3.09 97.0 25 6.5 0.07 or less 0.0124 0 Example 14 2.97 97.318 0 0.07 or less 0.0027 0 Example 15 2.96 97.2 21 0 0.07 or less 0.00270 Example 16 3.10 96.8 19 4 0.07 or less 0.0060 0 Example 17 3.07 96.826 5 0.07 or less 0.0030 0 Example 18 3.08 97.7 21 2.5 0.07 or less0.0022 0 Example 19 3.09 97.0 21 8 0.07 or less 0.0024 0 Example 20 2.9796.8 24 2 0.07 or less 0.0228 0 Example 21 2.99 97.0 18 10 0.07 or less0.0132 0 Example 22 3.00 97.2 17 0/2 0.07 or less 0.0027/0.0228 0Example 23 — — — 0 0.07 or less 0.0027 — Example 24 3.19 97.0 20 0  0.190.176 1 Comparative Example 1 2.98 97.7 19 13 0.07 or less 0.0168 0Comparative Example 2 2.99 97.8 17 18.5 0.07 or less 0.0176 0Comparative Example 3 2.96 97.5 18 11 0.07 or less 0.0030 0 ComparativeExample 4 2.99 97.6 18 11.5 0.07 or less 0.0028 0 Comparative Example 52.95 97.5 24 23 0.07 or less 0.0034 0 Comparative Example 6 2.98 97.3 2319 0.07 or less 0.0096 0 Comparative Example 7 2.99 96.7 23 Remained0.07 or less 0.0072 0 Comparative Example 8 3.02 97.0 19 deformed invinyl 0.07 or less 0.0172 0 Comparative Example 9 3.00 97.2 20 chlorideform and 0.07 or less 0.0027 0 did not return Comparative Example 103.67 93.8 226 13 0.07 or less 0.0168 0 Comparative Example 11 3.71 94.5155 23 0.07 or less 0.0034 0 Comparative Example 12 3.65 48.0 680 1925.88 — 3 Comparative Example 13 3.16 97.5 21 15 0.07 or less 0.0002 0Comparative Example 14 3.18 97.4 19 16 0.07 or less 0.0004 0 ComparativeExample 15 3.18 97.3 20 14 0.07 or less 0.0005 0

In Table 2, all the samples were able to stand by themselves by thesurface tension before measurement of “force applied per unit mass·unitarea (1)” and “force applied per unit a mass·unit area (2)” (i.e., didnot slip down).

In Comparative Examples 1, 2, 7 to 9, since the mass per unit area waslarge and the force applied per unit mass·unit area (1) was small, theadhesiveness to the membrane was poor. Thus, with a large electrolyzersize (e.g., 1.5 m in length and 3 m in width), the membrane, which is apolymer membrane, may be inevitably slacked during handling. In thistime, the electrode comes off and thus, the samples do not withstandpractical use.

In Comparative Examples 3 and 4, since the force applied per unitmass·unit area (1) was small, the adhesiveness to the membrane was poor.Thus, with a large electrolyzer size (e.g., 1.5 m in length and 3 m inwidth), the membrane, which is a polymer membrane, may be inevitablyslacked during handling. In this time, the electrode comes off and,thus, the samples do not withstand, practical use.

In Comparative Examples 5 and 6, the mass per unit area is large, andthe adhesiveness to the membrane was poor. Thus, with a largeelectrolyzer size (e.g., 1.5 m in length and 3 m in width), themembrane, which is a polymer membrane, may be inevitably slacked duringhandling. In this time, the electrode comes off and thus, the samples donot withstand practical use.

In Comparative Examples 10 and 11, since the membrane and the electrodewere tightly bonded by thermal pressing, the electrode did not come offfrom the membrane during handling like Comparative Examples 1, 2, 7 to9. However, due to the tight bonding to the electrode, the flexibilityof the polymer membrane was lost. Thus, it is difficult to roll thesamples into a roll and fold the samples. The samples have poor handlingproperty and do not withstand practical use.

Furthermore, in Comparative Examples 10 and 11, the electrolyticperformance significantly deteriorated. Conceivably, the voltagemarkedly increased because the flow of ions was inhibited by the factthat the electrode became embedded in the ion exchange membrane. Withrespect to the reason of the decrease in the current efficiency and thedegradation of the common salt concentration in caustic soda, possiblefactors included high current efficiency, occurrence of uneven thicknessor the carboxylic acid layer due to embedding the electrode in thecarboxylic acid layer having an effect of exhibiting ion selectivity,and penetration of the electrode embedded into a port the carboxylicacid layer.

Additionally, in Comparative Examples 10 and 11, in the case where aproblem occurred either in the membrane or the electrode and replacementwas required, it was not possible to replace one of the membrane and theelectrode due to the tight bonding, which led to a higher cost.

In Comparative Example the electrolytic performance significantlydeteriorated. Conceivably, the voltage mark increased because a productaccumulated on the interface between the membrane and the electrode.

In Comparative Examples 1 3 to 15, both the forces applied per unit massunit area (1) and (2) were small (equal to or less than the measurementlower limit), and thus, the adhesiveness to the membrane was poor. Thus,with a large electrolyzer size (e.g., 1.5 m in length and 3 m in width),the membrane, which is a polymer membrane, may be inevitably slackedduring handling. In this time, the electrode comes off and thus, thesamples do not withstand practical use.

In the present embodiment, the membrane and the electrode are in closecontact with each other on each surface with a moderate force, and thus,there are no problems such as coming-off of the electrode duringhandling. The flow of ions in the membrane is not inhibited, and thus,good electrolytic performance is exhibited.

<Verification of Second Embodiment>

As will be described below, Experiment Examples according to the secondembodiment (in the section of <Verification of second embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the second embodiment (in the section of <Verificationof second embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 31 to 42 asappropriate.

[Evaluation Method] (1) Opening Ratio

An electrode was cut into a size of 130 mm×100 mm. A digimatic thicknessgauge (manufactured by Mitutoyo Corporation, minimum scale 0.001 mm) wasused to calculate an average value of 10 points obtained by measuringevenly in the plane. The value was used as the thickness of theelectrode (gauge thickness) to calculate the volume. Thereafter, anelectronic balance was used to measure the mass. From the specificgravity of each metal (specific gravity of nickel=8.908 g/cm³, specificgravity of titanium=4.506 g/cm³), the opening ratio or void ratio wascalculated.

Opening ratio (Void ratio) (%)=(1−(electrode mass)/(electrodevolume×metal specific gravity))×100

(2) Mass per Unit Area (mg/cm²)

An electrode was cut into a size of 130 mm×100 mm, and the mass thereofwas measured by an electronic balance. The value was divided by the area(130 mm×100 mm) to calculate the mass per unit area.

(3) Force Applied per Unit Mass·Unit Area (1) (Adhesive Force)(N/mg·cm²))

[Method (i)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-6001 type load cell).

A 200 mm square nickel plate having a thickness of 1.2 mm was subjectedto blast processing with alumina of grain-size number 320. Thearithmetic average surface roughness (Ra) of the nickel plate after theblast treatment was 0.7 μm. For surface roughness measurement herein, aprobe type surface roughness measurement instrument SJ-310 (MitutoyoCorporation) was used. A measurement sample was placed on the surfaceplate parallel to the ground surface to measure the arithmetic averageroughness Ra under measurement conditions as described below. Themeasurement was repeated 6 times, and the average value was listed.

<Probe shape> conical taper angle=60°, tip radius=2 μm, static measuringforce=0.75 mN

<Roughness standard> JIS2001

<Evaluation curve> R

<Filter> GAUSS

<Cutoff value λc> 0.8 mm

<Cutoff value λs> 2.5

<Number of sections> 5

<Pre-running, post-running> available

This nickel plate was vertically fixed on the lower chuck of the tensileand compression testing machine.

As the membrane, an ion exchange membrane A below was used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTFE) were used (hereinafter referred to asPTFE yarns). As sacrifice yarns, yarns obtained by twisting six 35denier filaments of polyethylene terephthalate (PET) 200 times/m wereused (hereinafter referred to as PET yarns). First, in each of the TDand the MD, the PTFE yarns and the sacrifice yarns were plain-woven with24 PTFE yarns/inch so that two sacrifice yarns were arranged betweenadjacent PTFE yarns, to obtain a woven fabric. The resulting wovenfabric was pressure-bonded by a roll to obtain a woven fabric having athickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂=CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin B of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having a primary particle sizeof 1 μm was added to a 5% by mass ethanol solution of the acid-typeresin of the resin B and dispersed to prepare a suspension, and thesuspension was sprayed onto both the surfaces of the above compositemembrane by a suspension spray method to form coatings of zirconiumoxide on the surfaces of the composite membrane to obtain an ionexchange membrane A. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.5 mg/cm². The average particle sizewas measured by a particle size analyzer (manufactured by SHIMADZUCORPORATION, “SALD(R) 2200”).

The ion exchange membrane (membrane) obtained above was immersed in purewater for 12 hours or more and then used for the test. The membrane wasbrought into contact with the above nickel plate sufficiently moistenedwith pure water and allowed to adhere to the plate by the tension ofwater. At this time, the nickel plate and the ion exchange membrane wereplaced so as to align the upper ends thereof.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedby the upper chuck of the tensile and compression testing machine tohang the electrode. The load applied on the testing machine at this timewas set to 0 N. The integrated piece of the stainless plates, electrode,and clips was once removed from the tensile and compression testingmachine, and immersed in a vat containing pure water in order to moistenthe electrode sufficiently with pure water. Thereafter, the center ofthe stainless plates was clamped again by the upper chuck of the tensileand compression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the ion exchange membrane by the surfacetension of pure water. The size of the adhesive surface at this time was130 mm in width and 110 mm in length. Pure water in a wash bottle wassprayed to the electrode and the ion exchange membrane entirely so as tosufficiently moisten the membrane and the electrode again. Thereafter, aroller formed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess pure water. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the overlapping portion ofthe electrode and the membrane reached 130 mm in width and 100 mm inlength was recorded. This measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion ofthe electrode and the ion exchange membrane and the mass of theelectrode of the portion overlapping the ion exchange membrane tocalculate the force applied per unit mass·unit area (1). The mass of theelectrode of the portion overlapping the ion exchange membrane wasdetermined through proportional calculation from the value obtained in(2) Mass per unit area (mg/cm²) described above.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was 30±5%.

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to the ion exchange membrane that adhered to avertically fixed nickel plate via the surface tension.

A schematic view of a method for evaluating the force applied is shownin FIG. 31.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(4) Force Applied per Unit Mass·Unit Area (2) (Adhesive Force)(N/mg·cm²))

[Method (ii)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-6001 type load cell).

A nickel plate identical to that in Method (i) was vertically fixed onthe lower chuck of the tensile and compression testing machine.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedby the upper chuck of the tensile and compression testing machine tohang the electrode. The load applied on the testing machine at this timewas set to 0 N. The integrated piece of the stainless plates, electrode,and clips was once removed from the tensile and compression testingmachine, and immersed in a vat containing pure water in order to moistenthe electrode sufficiently with pure water. Thereafter, the center ofthe stainless plates was clamped again by the upper chuck of the tensileand compression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the nickel plate via the surface tension of asolution. The size of the adhesive surface at this time was 130 mm inwidth and 110 mm in length. Pure water in a wash bottle was sprayed tothe electrode and the nickel plate entirely so as to sufficientlymoisten the nickel plate and the electrode again. Thereafter, a rollerformed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess solution. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the overlapping portion ofthe electrode and the nickel plate in the longitudinal direction reached100 mm was recorded. This measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion ofthe electrode and the nickel plate and the mass of the electrode of theportion overlapping the nickel plate to calculate the force applied perunit mass·unit area (2). The mass of the electrode of the portionoverlapping the membrane was determined through proportional calculationfrom the value obtained in (2) Mass per unit area (mg/cm²) describedabove.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was 30±5%.

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to a vertically-fixed nickel plate via the surfacetension.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(5) Method for Evaluating Winding Around Column of 280 mm in Diameter(1) (%) (Membrane and Column)

The evaluation method (1) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square. The ion exchange membrane was immersed in purewater for 12 hours or more and then used for the test. In ComparativeExamples 1 and 2, the electrode had been integrated with the ionexchange membrane by thermal pressing, and thus, an integrated piece ofan ion exchange membrane and an electrode was provided (electrode of a130 mm square). After the ion exchange membrane was sufficientlyimmersed in pure water, the membrane was placed on the curved surface ofa plastic (polyethylene) pipe having an outer diameter of 280 mm.Thereafter, excess solution was removed with a roller formed by windinga closed-cell type EPDM sponge rubber having a thickness of 5 mm arounda vinyl chloride pipe (outer diameter: 38 mm). The roller was rolledover the ion exchange membrane from the left to the right of theschematic view shown in FIG. 32. The roller was rolled only once. Oneminute after, the proportion of a portion at which the ion exchangemembrane was brought into a close contact with the plastic pipeelectrode having an outer diameter of 280 mm was measured.

(6) Method for Evaluating Winding Around Column of 280 mm in Diameter(2) (%) (Membrane and Electrode)

The evaluation method (2) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 280 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 33 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(7) Method for Evaluating Winding Around Column of 145 mm in Diameter(3) (%) (Membrane and Electrode)

The evaluation method (3) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 145 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 34 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(8) Handling Property (Response Evaluation)

(A) The ion exchange membrane A (membrane) produced in [Method (i)] wascut into a 170 mm square, and the electrode was cut into a size of95×110 mm. The ion exchange membrane was immersed in pure water for 12hours or more and then used for the test. In each Example, the ionexchange membrane and electrode were sufficiently immersed in threesolutions: sodium bicarbonate aqueous solution, 0.1N NaOH aqueoussolution, and pure water, then laminated, and placed still on a Teflonplate. The interval between the anode cell and the cathode cell used inthe electrolytic evaluation was set at about 3 cm. The laminate placedwas lifted, and an operation of inserting and holding the laminatetherebetween was conducted. This operation was conducted while theelectrode was checked for dislocation and dropping.

(B) The ion exchange membrane A (membrane) produced in [Method (i)] wascut into a 170 mm square, and the electrode was cut into a size of95×110 mm. The ion exchange membrane was immersed in pure water for 12hours or more and then used for the test. In each Example, the ionexchange membrane and electrode were sufficiently immersed in threesolutions: a sodium bicarbonate aqueous solution, a 0.1N NaOH aqueoussolution, and pure water, then laminated, and placed still on a Teflonplate. The adjacent two corners of the membrane portion of the laminatewere held by hands to lift the laminate so as to be vertical. The twocorners held by hands were moved from this state to be close to eachother such that the membrane was protruded or recessed. This move wasrepeated again to check the conformability of the electrode to themembrane. The results were evaluated on a four level scale of 1 to 4 onthe basis of the following indices:

1: good handling property

2: capable of being handled

3: difficult to handle

4: substantially incapable of being handled

Here, the sample of Comparative Example 2-5, provided in a sizeequivalent to that of a large electrolytic cell including an electrodein a size of 1.3 m×2.5 m and an ion exchange membrane in a size of 1.5m×2.8 m, was subjected to handling. The evaluation result of ComparativeExample 5 (“3” as described below) was used as an index to evaluate thedifference between the evaluation of the above (A) and (B) and that ofthe large-sized one. That is, in the case where the evaluation result ofa small laminate was “1” or “2”, it was judged that there was no problemin the handling property even if the laminate was provided in a largersize.

(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%), CommonSalt Concentration in Caustic Soda (ppm, on the Basis of 50%))

The electrolytic performance was evaluated by the following electrolyticexperiment.

A titanium anode cell having an anode chamber in which an anode wasprovided (anode terminal cell) and a cathode cell having a nickelcathode chamber in which a cathode was provided (cathode terminal cell)were oppositely disposed. A pair of gaskets was arranged between thecells, and a laminate (a laminate of the ion exchange membrane A and anelectrode for electrolysis) was sandwiched between the gaskets. Then,the anode cell, the gasket, the laminate, the gasket, and the cathodewere brought into close contact together to obtain an electrolytic cell,and an electrolyzer including the cell was provided.

The anode was produced by applying a mixed solution of rutheniumchloride, iridium chloride, and titanium tetrachloride onto a titaniumsubstrate subjected to blasting and acid etching treatment as thepretreatment, followed by drying and baking. The anode was fixed in theanode chamber by welding. As the cathode, one described in each ofExamples and Comparative Examples was used. As the collector of thecathode chamber, a nickel expanded metal was used. The collector had asize of 95 mm in length×110 mm in width. As a metal elastic body, amattress formed by knitting nickel fine wire was used. The mattress asthe metal elastic body was placed on the collector. Nickel mesh formedby plain-weaving nickel wire having a diameter of 150 μm in a sieve meshsize of 40 was placed thereover, and a string made of Teflon(R) was usedto fix the four corners of the Ni mesh to the collector. This Ni meshwas used as a feed conductor. This electrolytic cell has a zero-gapstructure by use of the repulsive force of the mattress as the metalelastic body. As the gaskets, ethylene propylene diene (EPDM) rubbergaskets were used. As the membrane, the ion exchange membrane A (160 mmsquare) produced in [Method (i)] was used.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted so as to allow the temperature in each electrolytic cell toreach 90° C. Common salt electrolysis was performed current density of 6kA/m² to measure the voltage, current efficiency, and common saltconcentration in caustic soda. The current efficiency here is theproportion of the amount of the produced caustic soda to the passedcurrent and when impurity ions and hydroxide ions rather than sodiumions move through the ion exchange membrane due to the passed current,the current efficiency decreases. The current efficiency was obtained bydividing the number of moles of caustic soda produced for a certain timeby the number of moles of the electrons of the current passing duringthat time. The number of moles of caustic soda was obtained byrecovering caustic soda produced by the electrolysis in a plasticcontainer and measuring its mass. As the common salt concentration incaustic soda, value obtained by converting the caustic sodaconcentration on the basis of 50% was shown.

The specification of the electrode and the feed conductor used in eachof Examples and Comparative Examples is shown Table 3.

(11) Measurement Thickness of Catalytic Layer, Substrate for Electrodefor Electrolysis, and Thickness of Electrode

For the thickness of the substrate for electrode for electrolysis, adigimatic thickness gauge (manufactured by Mitutoyo Corporation, minimumscale 0.001 mm) was used to calculate an average value of 10 pointsobtained by measuring evenly in the plane. The value was used as thethickness of the substrate for electrode for electrolysis (gaugethickness). For the thickness of the electrode, a digimatic thicknessgauge was used to calculate an average value of 10 points obtained bymeasuring evenly in the plane, in the same manner as for the substratefor electrode. The value was used as the thickness of the electrode(gauge thickness). The thickness of the catalytic layer was determinedby subtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode.

(12) Elastic Deformation Test of Electrode

The ion exchange membrane A (membrane) and the electrode produced in[Method (i)] were each cut into a 110 mm square. The ion exchangemembrane was immersed pure water for 12 hours or more and then used forthe test. After the ion exchange membrane and the electrode werelaminated to produce a laminate under conditions of a temperature: 23±2°C. and a relative humidity: 30+5%, the laminate was wound around a PVCpipe having an outer diameter of ϕ32 mm and a length of 20 cm withoutany gap, as shown in FIG. 35. The laminate was fixed using apolyethylene cable tie such that the laminate wound did not come offfrom the PVC pipe or loosen. The laminate was retained in this state for6 hours. Thereafter, the cable tie was removed, and the laminate wasunwound from the PVC pipe. Only the electrode was placed on a surfaceplate, and the heights L₁ and L₂ of a portion lifted from the surfaceplate were measured to determine an average value. This value was usedas the index of the electrode deformation. That is, a smaller valuemeans that the laminate is unlikely to deform.

When an expanded metal is used, there are two winding direction: the SWdirection and the LW direction. In this test, the laminate was wound inthe SW direction.

Deformed electrodes (electrodes that did not return to their originalflat state) were evaluated for softness after plastic deformation inaccordance with a method as shown in FIG. 36. That is a deformedelectrode was placed on a membrane sufficiently immersed pure water. Oneend of the electrode was fixed and the other lifted end was pressed ontothe membrane to release a force, and an evaluation was performed whetherthe deformed electrode conformed to the membrane.

(13) Membrane Damage Evaluation

As the membrane, an ion exchange membrane B below was used.

As reinforcement core materials those obtained by twisting 100 deniertape yarns of polytetrafluoroethylene (PTFE) 900 times/m into a threadform were used (hereinafter referred to as PTFE yarns). As warpsacrifice yarns, yarns obtained by twist ng eight 35 denier filaments ofpolyethylene terephthalate (PET) 200 times/m were used (hereinafterreferred to as PET yarns). As weft sacrifice yarns, yarns obtained bytwisting eight 35 denier filaments of polyethylene terephthalate (PET)200 times/m were used. First, the PTFE yarns and the sacrifice yarnswere plain-woven with 24 PTFE yarns/inch so that two sacrifice yarnswere arranged between adjacent PTFE yarns, to obtain a woven fabrichaving a thickness of 100 μm.

Next, a polymer (A1) of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.92mg equivalent/g and a polymer (B1) of a dry resin that was a copolymerof CF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g were provided. Using these polymers(A1) and (B1), a two-layer film X in which the thickness of a polymer(A1) layer was 25 μm and the thickness of a polymer (B1) layer was 89 μmwas obtained by a coextrusion T die method. As the ion exchange capacityof each polymer, shown was the ion exchange capacity in the case ofhydrolyzing the ion exchange group precursors of each polymer forconversion into ion exchange groups.

Separately, a polymer (B2) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g was provided. This polymer wassingle-layer extruded to obtain a film Y having a thickness of 20 μm.

Subsequently, release paper, the film Y, a reinforcing material, and thefilm X were laminated in this order on a hot plate having a heat sourceand a vacuum source inside and having micropores on its surface, heatedand depressurized under the conditions of a hot plate temperature of225° C. and a degree of reduced pressure of 0.022 MPa for two minutes,and then the release paper was removed to obtain a composite membrane.The resulting composite membrane was immersed in an aqueous solutioncomprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) foran hour for saponification. Thereafter, the membrane was immersed in0.5N NaOH for an hour to replace the ions attached to the ion exchangegroups by Na, and then washed with water. Further, the membrane wasdried at 60° C.

Additionally, a polymer (B3) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.05 mg equivalent/g were hydrolyzed and then was turnedinto an acid type with hydrochloric acid. Zirconium oxide particleshaving an average particle size of primary particles of 0.02 μm wereadded to a 50/50 (mass ratio) mixed solution of water and ethanol inwhich the polymer (B3′) of this acid type was dissolved in a proportionof 5% by mass such that the mass ratio of the polymer (B3′) to thezirconium oxide particles was 20/80. Thereafter, the polymer (B3′) wasdispersed in a suspension of the zirconium oxide particles with a ballmill to obtain a suspension.

This suspension was applied by a spray method onto both the surfaces ofthe ion exchange membrane and dried to obtain an ion exchange membrane Bhaving a coating layer containing the polymer (B3′) and the zirconiumoxide particles. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.35 mg/cm².

The anode used was the same as in (9) Electrolytic evaluation.

The cathode used was one described in each of Examples and ComparativeExamples. The collector, mattress, and feed conductor of the cathodechamber used were the same as in (9) Electrolytic evaluation. That is, azero-gap structure had been provided by use of Ni mesh as the feedconductor and the repulsive force of the mattress as the metal elasticbody. The gaskets used were the same as in (9) Electrolytic evaluation.As the membrane, the ion exchange membrane B produced by the methodmentioned above was used. That is, an electrolyzer equivalent to that in(9) was provided except that the laminate of the ion exchange membrane Band the electrode for electrolysis was sandwiched between a pair ofgaskets.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted such that the temperature in each electrolytic cell reached 70°C. Common salt electrolysis was performed at a current density of 8kA/m². The electrolysis was stopped 12 hours after the start of theelectrolysis, and the ion exchange membrane B was removed and observedfor its damage condition.

“0” means no damage “1 to 3” means that damage was present, and a largernumber means a larger degree of damage.

(14) Ventilation Resistance of Electrode

The ventilation resistance of the electrode was measured using an airpermeability tester KES-F8 (trade name, KATO TECH CO., LTD.). The unitfor the ventilation resistance value is kPa·s/m. The measurement wasrepeated 5 times, and the average value was listed in Table 4. Themeasurement was conducted under the following two conditions. Thetemperature of the measuring chamber was 24° C. and the relativehumidity was 32%.

Measurement Condition 1 (Ventilation Resistance 1)

Piston speed: 0.2 cm/s

Ventilation volume: 0.4 cc/cm²/s

Measurement range: SENSE L (low)

Sample size: 50 mm×50 mm

Measurement Condition 2 (Ventilation Resistance 2)

Piston speed: 2 cm/s

Ventilation volume: 4 cc/cm²/s

Measurement range: SENSE M (medium) or H (high)

Sample size: 50 mm×50 mm

Example 2-1

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 16 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.71 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching. The opening ratio was 49%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a poly chloride (PVC) cylinder was always incontact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced in Example 2-1 was 24μm. The thickness of the catalytic layer, which was determined bysubtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode, was 8 μm. The coatingwas formed also on the surface not roughened. The thickness was thetotal thickness of ruthenium oxide and cerium oxide.

The measurement results of the adhesive force of the electrode producedby the above method are shown in Table 4. A sufficient adhesive forcewas observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The roughenedsurface of the electrode was oppositely disposed on a substantial centerposition of the carboxylic acid layer side of the ion. exchange membraneA (size: 160 mm×160 mm), produced in [Method (i)] and equilibrated witha 0.1 N NaOH aqueous solution, and allowed to adhere thereto via thesurface tension of the aqueous solution.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The above membrane-integrated electrode was sandwiched between the anodecell and the cathode cell such that the surface onto which the electrodewas attached was allowed to face the cathode chamber side. In thesectional structure, the collector, the mattress, the nickel mesh feedconductor, the electrode, the membrane, and the anode are arranged inthe order mentioned from the cathode chamber side to form a zero-gapstructure.

The resulting electrode was subjected to electrolytic evaluation. Theresults are shown in Table 4.

The electrode exhibited a low voltage, high current efficiency, and alow common salt concentration in caustic soda. The handling property wasalso good: “1”. The membrane damage was also evaluated as good: “0”.

When the amount of coating after the electrolysis was measured byfluorescent X-ray analysis (XRF), substantially 100% of the coatingremained on the roughened surface, and the coating on the surface notroughened was reduced. This indicates that the surface opposed to themembrane (roughened surface) contributes to the electrolysis and theother surface not opposed to the membrane can achieve satisfactoryelectrolytic performance when the amount of coating is small or nocoating is present.

Example 2-2

In Example 2-2, an electrolytic nickel foil having a gauge thickness of22 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 0.96 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 2-1, and theresults are shown in Table 4.

The thickness of the electrode was 29 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 7 82 m. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0033 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 2-3

In Example 2-3, an electrolytic nickel foil having a gauge thickness or30 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel platinum. The arithmetic average roughnessRa of the roughened surface was 1.38 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 2-1, and theresults are shown in Table 4.

The thickness of the electrode was 38 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 8 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating small or no coating is present.

Example 2-4

In Example 2-4, an electrolytic nickel foil having a gauge thickness of16 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to a roughening treatmentmeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 0.71 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 75%. Except for the above described,evaluation was performed in the same manner as in Example 2-1, and theresults are shown in Table 4.

The thickness of the electrode was 24 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 8 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 2-5

In Example 2-5, an electrolytic nickel foil having a gauge thickness of20 μm was provided as the substrate for electrode for cathodeelectrolysis. Both the surface of this nickel foil was subjected to aroughening treatment by means of electrolytic nickel plating. Thearithmetic average roughness Ra of the roughened surface was 0.96 μm.Both the surfaces had the same roughness. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 49%. Except for the above described,evaluation was performed in the same manner as in Example 2-1, and theresults are shown in Table 4.

The thickness of the electrode was 30 μm. The thickness of the catalystlayer, which was determined by subtract ng the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Additionally, when the amount of coating after the electrolysis wasmeasured by XRF, substantially 100% of the coating remained on both thesurfaces. In consideration of comparison with Examples 2-1 to 2-4, thisindicates that the other surface not opposed to the membrane can achievesatisfactory electrolytic performance when the amount of coating issmall or no coating is present.

Example 2-6

In Example 2-6, evaluation was performed in the same manner as inExample 2-1 except that coating of the substrate for electrode forcathode electrolysis was performed by ion plating, and the results areshown in Table 4. In the ion plating, film forming was performed using aheating temperature of 200° C. and Ru metal target under an argon/oxygenatmosphere at a film forming pressure of 7×10² Pa. The coating formedwas ruthenium oxide.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-7

In Example 2-7, the substrate for electrode for cathode electrolysis wasproduced by an eletroforming method. The photomask ad a shape formed byvertically and horizontally arranging 0.485 mm×0.485 mm squares at aninterval of 0.15 mm. Exposure, development, and electroplating weresequentially performed to obtain a nickel porous foil having a gaugethickness of 20 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.71 μm. The measurement of the surfaceroughness was performed under the same condition as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 37 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 17 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-8

In Example 2-8, the substrate for electrode for cathode electrolysis wasproduced by an electroforming method. The substrate had a gaugethickness of 50 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.73 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 60 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: The membrane damage was also evaluatedas good: “0”.

Example 2-9

In Example 2-9, a nickel nonwoven fabric having a gauge thickness of 150μm and a void ratio of 76% (manufactured NIKKO TECHNO, Ltd.) was used asthe substrate for electrode for cathode electrolysis. The nonwovenfabric had a nickel fiber diameter of about 40 μm and a basis weight of300 g/m². Except for the above described, evaluation was performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 165 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 29 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0612 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 2-10

In Example 2-10, a nickel nonwoven fabric having a gauge thickness of200 μm and a void ratio of 72% (manufactured by NIKKO TECHNO, Ltd.) wasused as the substrate for electrode for cathode electrolysis. Thenonwoven fabric had a nickel fiber diameter of about 40 μm and a basisweight of 500 g/m². Except for the above described, evaluation wasperformed in the same manner as in Example 2-1, and the results areshown in Table 4.

The thickness of the electrode was 215 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 40 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0164 (kPa·s/m) under the measurement condition 2

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 2-11

In Example 2-11, foamed nickel having a gauge thickness of 200 μm and avoid ratio of 72% (manufactured by Mitsubishi Materials Corporation) wasused as the substrate for electrode for cathode electrolysis. Except forthe above described, evaluation was performed in the same manner as inExample 2-1, and the results are shown in Table 4.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 17 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0402 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 2-12

In Example 2-12, a 200-mesh nickel mesh having a line diameter of 50 μm,a gauge thickness of 100 μm, and an opening ratio of 37% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didnot change the opening ratio. It is difficult to measure the roughnessof the surface of the metal net. Thus, in Example 2-12, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra of a wire piece of the wire mesh was0.64 μm. The measurement of the surface roughness was performed underthe same conditions as for the surface roughness measurement of thenickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-1, and the results are shown in Table 4.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0154 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage wasevaluated as good: “0”.

Example 2-13

In Example 2-13, a 150-mesh nickel mesh having a line diameter of 65 μm,a gauge thickness of 130 μm, and an opening ratio of 38% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didnot change the opening ratio. It is difficult to measure the roughnessof the surface of the metal net. Thus, in Example 2-13, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.66 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 2-1, and the results areshown in Table 4.

The thickness of the electrode was 133 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 3 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 6.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0124 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, nigh currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was also evaluatedas good: “0”.

Example 2-14

In Example 2-14, a substrate identical to that of Example 2-3 (gaugethickness of 30 μm and opening ratio of 44%) was used as the substratefor electrode for cathode electrolysis. Electrolytic evaluation wasperformed with a structure identical to that of Example 2-1 except thatno nickel mesh feed conductor was included. That is, in the sectionalstructure of the cell, the collector, the mattress, themembrane-integrated electrode, and the anode are arranged in the ordermentioned from the cathode chamber side to form a zero-gap structure,and the mattress serves as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-1, and the results are shown in Table 4.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-15

In Example 2-15, a substrate identical to that of Example 2-3 (gaugethickness of 30 μm and opening ratio of 44%) was used as the substratefor electrode for cathode electrolysis. The cathode used in ReferenceExample 1, which was degraded and had an enhanced electrolytic voltage,was placed instead of the nickel mesh feed conductor. Except for theabove described, electrolytic evaluation was performed with a structureidentical to that of Example 2-1. That is, in the sectional structure ofthe cell, the collector, the mattress, the cathode that was degraded andhad an enhanced electrolytic voltage (serves as the feed conductor), theelectrode for electrolysis (cathode), the membrane, and the anode arearranged in the order mentioned from the cathode chamber side to form azero-gap structure, and the cathode that is degraded and has an enhancedelectrolytic voltage serves as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-1, and the results are shown in Table 4.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less, under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-16

A titanium foil having a gauge thickness of 20 μm was provided as thesubstrate for electrode for anode electrolysis. Both the surfaces of thetitanium foil were subjected to a roughening treatment. A porous foilwas formed by perforating this titanium toil with circular holes bypunching. The hole diameter was 1 mm, and the opening ratio was 14%. Thearithmetic average roughness Ra of the surface was 0.37 μm. Themeasurement of the surface roughness was performed under the sameconditions as for the surface roughness measurement of the nickel platesubjected to the blast treatment.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPM (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied ballowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).After the above coating liquid was applied onto the titanium porousfoil, drying at 60° C. for 10 minutes and baking at 475° C. for 10minutes were performed. A series of these coating, drying, preliminarybaking, and baking operations was repeatedly performed, and then bakingat 520° C. was performed for an hour.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The cutelectrode was allowed to adhere via the surface tension of the aqueoussolution to a substantial center position of the sulfonic acid layerside of the ion exchange membrane A (size: 160 mm×160 mm) produced in[Method (i)] and equilibrated with a 0.1 N NaOH aqueous solution.

The cathode was prepared in the following procedure. First, a 40-meshnickel wire mesh having a line diameter of 150 μm was provided as thesubstrate. After blasted with alumina as pretreatment, the wire mesh wasimmersed in 6 N hydrochloric acid for 5 minutes, sufficiently washedwith pure water, and dried.

Next, a ruthenium chloride solution having a ruthenium concentration of100 g/L (Tanaka Kikinzoku Kogyo K.K.) and cerium chloride (KISHIDACHEMICAL Co., Ltd.) were mixed such that the molar ratio between theruthenium element and the cerium element was 1:0.25. This mixed solutionwas sufficiently stirred and used as a cathode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 300°C. for 3 minutes, and baking at 550° C. for 10 minutes were performed.Thereafter, baking at 550° C. for an hour was performed. A series ofthese coating, drying, preliminary baking, and baking operations wasrepeated.

As the collector of the cathode chamber, a nickel expanded metal wasused. The collector had a size of 95 mm in length×110 mm in width. As ametal elastic body, a mattress formed by knitting nickel fine wire wasused. The mattress as the metal elastic body was placed on thecollector. The cathode produced by the above method was placedthereover, and a string made of Teflon(R) was used to fix the fourcorners of the mesh to the collector.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the anodes, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did riot come off or was notdisplaced.

The anode used in Reference Example 3, which was degraded and had anenhanced electrolytic voltage, was fixed to the anode cell welding, andthe above membrane-integrated electrode was sandwiched between the anodecell and the cathode cell such that the surface onto which the electrodewas attached was allowed to face the anode chamber side. That is, in thesectional structure of the cell, the collector, the mattress, thecathode, the membrane, the electrode for electrolysis (titanium porousfoil anode), and the anode that was degraded and had an enhancedelectrolytic voltage were arranged in the order mentioned from thecathode chamber side to form a zero-gap structure. The anode that wasdegraded and had an enhanced electrolytic voltage served as the feedconductor. The titanium porous foil anode and the anode that wasdegraded and had an enhanced electrolytic voltage were only in physicalcontact with each other and were not fixed with each other by welding.

Evaluation on this structure was performed in the same manner as inExample 2-1, and the results are shown in Table 4.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 6 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 4 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition and 0.0060 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-17

In Example 2-17%, a titanium foil having a gauge thickness of 20 μm andan opening ratio of 30% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.37 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-16, and the results are shown in Table 4.

The thickness of the electrode was 30 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 5 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: The membrane damage was also evaluatedas good: “0”.

Example 2-18

In Example 2-18, a titanium foil having a gauge thickness of 20 μm andan opening ratio of 42% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.38 μm. The measurement of the surface roughness was per formedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-16, and the results are shown in Table 4.

The thickness of the electrode was 32 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 12 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0022 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-19

In Example 2-19, a titanium foil having a gauge thickness of 50 μm andan opening ratio of 47% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.40 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-16, and the results are shown in Table 4.

The thickness of the electrode was 69 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 19 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 8 μm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0024 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-20

In Example 2-20, a titanium nonwoven fabric having a gauge thickness of100 μm, a titanium fiber diameter of about 20 μm, a basis weight of 100g/m², and an opening ratio of 78% was used as the substrate forelectrode for anode electrolysis. Except for the above described,evaluation was performed in the same manner as in Example 2-16, and theresults are shown in Table 4.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0228 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-21

In Example 2-21, a 150-mesh titanium wire mesh having a gauge thicknessof 120 μm and a titanium fiber diameter of about 60 μm was used as thesubstrate for electrode for anode electrolysis. The opening ratio was42%. A blast treatment was performed with alumina of grain-size number320. It is difficult to measure the roughness of the surface of themetal net. Thus, in Example 2-21, a titanium plate having a thickness of1 mm was simultaneously subjected to the blast treatment during theblasting, and the surface roughness of the titanium plate was taken asthe surface roughness of the wire mesh. The arithmetic average roughnessRa was 0.60 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example2-16, and the results are shown in Table 4.

The thickness of the electrode was 140 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 20 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 10 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0132 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 2-22

In Example 2-22, an anode that was degraded and had an enhancedelectrolytic voltage was used in the same manner as in Example 2-16 asthe anode feed conductor, and a titanium nonwoven fabric identical tothat of Example 2-20 was used as the anode. A cathode that was degradedand had an enhanced electrolytic voltage was used in the same manner asin Example 2-15 as the cathode feed conductor, and a nickel foilelectrode identical to that of Example 2-3 was used as the cathode. Inthe sectional structure of the cell, the collector, the mattress, thecathode that was degraded and had an enhanced voltage, the nickel porousfoil cathode, the membrane, the titanium nonwoven fabric anode, and theanode that was degraded and had an enhanced electrolytic voltage arearranged in the order mentioned from the cathode chamber side to form azero-gap structure, and the cathode and anode degraded and having anenhanced electrolytic voltage serve as the feed conductor. Except forthe above described, evaluation was performed in the same manner as inExample 2-1, and the results are shown in Table 4.

The thickness of the electrode (anode) was 114 μm, and the thickness thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode (anode), was 14 μm. The thickness of the electrode (cathode)was 38 μm, and the thickness of the catalytic layer, which wasdetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electrode (cathode), was 8μm.

A sufficient adhesive force was observed both in the anode and thecathode.

When a deformation test of the electrode (anode) was performed, theaverage value of L₁ and L₂ was 2 mm. When a deformation test of theelectrode (cathode) was performed, the average value of L₁ and L₂ was 0mm.

When the ventilation resistance of the electrode (anode) was measured,the ventilation resistance was 0.07 (kPa·s/m) or less under themeasurement condition and 0.0228 (kPa·s/m) under the measurementcondition 2. When the ventilation resistance of the electrode (cathode)was measured, the ventilation resistance was 0.07 (kPa·s/m) or lessunder the measurement condition 1 and 0.0027 (kPa·s/m) under themeasurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0” both in the anode and the cathode. In Example2-22, the cathode and the anodes were combined by attaching the cathodeto one surface of the membrane and the anode o the other surface andsubjected to the membrane damage evaluation.

Example 2-23

In Example 2-23, a microporous membrane “Zirfon Perl UTP 500”manufactured by Agfa was used.

The Zirfon membrane was immersed in pure water for 12 hours or more andused for the test. Except for the above described, the above evaluationwas performed in the same manner as in Example 2-3, and the results areshown in Table 4.

When a deformation test the electrode was performed, the average valueof L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

Similarly to the case where an ion exchange membrane was used as themembrane, a sufficient adhesive force was observed. The microporousmembrane was brought into a close contact with the electrode via thesurface tension, and the handling property was good: “1”.

Example 2-24

A carbon cloth obtained by weaving a carbon fiber having a gaugethickness of 566 μm was provided as substrate for electrode for cathodeelectrolysis coating liquid for use in forming an electrode catalyst onthis carbon cloth was prepared by the following procedure. A rutheniumnitrate solution having a ruthenium concentration of 100 g/L (FURUYAMETAL Co., Ltd.) and cerium nitrate (KISHIDA CHEMICAL Co., Ltd.) weremixed such that the molar ratio between the ruthenium element and thecerium element was 1:0.25. This mixed solution was sufficiently stirredand used as a cathode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088 (tradename), thickness 10 mm) around a chloride (PVC) cylinder was always incontact with the above coating liquid. A coating roll around which thesame EPDM had been wound was laced at the upper portion thereof, and aPVC roller was further placed thereabove. The coating liquid was appliedby allowing the substrate for electrode to pass between the secondcoating roll and the PVC roller at the uppermost portion (roll coatingmethod). Then, after drying at 50° C. for 10 minutes, preliminary bakingat 150° C. for 3 minutes, and baking at 350° C. for 10 minutes wereperformed. A series of these coatrig, drying, preliminary baking, andbaking operations was repeated until a predetermined amount of coatingwas achieved. The thickness of the electrode produced was 570 μm. Thethickness of the catalytic layer, which was determined by subtractingthe thickness of the substrate for electrode for electrolysis from thethickness of the electrode, was 4 μm. The thickness of the catalyticlayer was the total thickness of ruthenium oxide and cerium oxide.

The resulting electrode was subjected to electrolytic evaluation. Theresults are shown in Table 4.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.19 (kPa·s/m) under the measurementcondition 1 and 0.176 (kPa·s/m) under the measurement condition 2.

The electrode had a handling property of “2” and was determined to behandleable as a large laminate.

The voltage was high, the membrane damage was evaluated as “1”, andmembrane damage was observed. It was conceived that this is because NaOHthat had been generated in the electrode accumulated on the interfacebetween the electrode and the membrane to elevate the concentrationthereof, due to the high ventilation resistance of the electrode ofExample 2-24.

Reference Example 1

In Reference Example 1, used was a cathode used as the cathode in alarge electrolyzer for eight years, degraded, and having an enhancedelectrolytic voltage. The above cathode was placed instead of the nickelmesh feed conductor on the mattress of the cathode chamber, and the ionexchange membrane A produced in [Method (i)] was sandwichedtherebetween. Then, electrolytic evaluation was performed. In ReferenceExample 1, no membrane-integrated electrode was used. In the sectionalstructure of the cell, the collector, the mattress, the cathode that wasdegraded and had an enhanced electrolytic voltage, the ion exchangemembrane A, and the anodes were arranged in the order mentioned from thecathode chamber side to form a zero-gap structure,

As a result of the electrolytic evaluation that with this structure, thevoltage was 3.04 V, the current efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was20 ppm. Consequently, due to degradation of the cathode, the voltage washigh.

Reference Example 2

In Reference Example 2, a nickel mesh feed conductor was used as thecathode. That electrolysis was performed on nickel mesh having nocatalyst coating thereon.

The nickel mesh cathode was placed on the mattress of the cathodechamber, and the ion exchange membrane A produced in [Method (i)] wassandwiched therebetween. Then, electrolytic evaluation was performed. Inthe sectional structure of the electric cell of Reference Example 2, thecollector, the mattress, the nickel mesh, the ion exchange membrane A,and the anodes were arranged in the order mentioned from the cathodechamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.38 V, the current efficiency was 97.7%, the common saltconcentration in caustic soda (value converted on the basis of 50%) wasppm. Consequently, the voltage was high because the cathode catalyst hadno coating.

Reference Example 3

In Reference Example 3, used was an anode used as the anode in a largeelectrolyzer for about eight years, degraded, and having an enhancedelectrolytic voltage.

In the sectional structure of the electrolytic cell of Reference Example3, the collector, the mattress, the cathode, the ion exchange membrane Aproduced in [Method (i)], and the anode that was degraded and had anenhanced electrolytic voltage were arranged in the order mentioned fromthe cathode chamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.18 V, the current efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was22 ppm. Consequently, due to degradation of the anode, the voltage washigh.

Example 2-25

In Example 2-25, a fully-rolled nickel expanding metal having a gaugethickness of 100 μm and an opening ratio of 33% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-25, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.68 μm. The measurement of thesurface roughness m performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

The mass per unit area was 67.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.05 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was 64%, and the result of evaluation of winding around column of 145 mmin diameter (3) was 22%. The portions at which the electrode came offfrom the membrane increased. This is because there were problems in thatthe electrode was likely to come off when the membrane-integratedelectrode was handled and in that the electrode came off and fell fromthe membrane during handled. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Example 2-26

In Example 2-26, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 16% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-26, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.64 μm. The measurement of thesurface roughness m performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation as performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 107 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm.

The mass per unit area was 78.1 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.04 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was 37%, and the result of evaluation of winding around column of 145 mmin diameter (3) was 25%. The portions at which the electrode came offfrom the membrane increased. This is because there were problems in thatthe electrode was likely to come off when the membrane-integratedelectrode was handled and in that the electrode came off and fell fromthe membrane during handled. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 18.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0176 (kPa·s/m) under the measurement condition 2.

Example 2-27

In Example 2-27, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 40% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot chanced after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-27, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.70 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Coating of the substrate for electrode for electrolysis wasperformed by ion plating in the same manner as in Example 2-6. Exceptfor the above described, evaluation was performed in the same manner asin Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

The force applied per unit mass·unit area (1) was such a small value as0.07 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter (2) was 80%, and the result of evaluation ofwinding around column of 145 mm in diameter (3) was 32%. The portions atwhich the electrode came off from the membrane increased. This isbecause there were problems in that the electrode was likely to come offwhen the membrane-integrated electrode was handled and in that theelectrode came off and fell from the membrane during handled. Thehandling property was “3”, which was also problematic. The membranedamage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Example 2-28

In Example 2-28, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 58% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-28, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.64 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 2-1, and the results are shown in Table 4.

The thickness of the electrode was 109 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 9 μm.

The force applied per unit mass·unit area (1) was such a small value as0.06 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter (2) was 69%, and the result of evaluation ofwinding around column of 145 mm in diameter (3) was 39%. The portions atwhich the electrode came off from the membrane increased. This isbecause there were problems in that the electrode was likely to come offwhen the membrane-integrated electrode was handled and in that theelectrode came off and fell from the membrane during handled. Thehandling property was “3”, which was also problematic. The membranedamage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

Example 2-29

In Example 2-29, a nickel wire mesh having a gauge thickness of 300 μmand an opening ratio of 56% was used as the substrate for electrode forcathode electrolysis. It is difficult to measure the surface roughnessof the wire mesh. Thus, in Example 2-29, a nickel plate having athickness of 1 mm was simultaneously subjected to the blast treatmentduring the blasting, and the surface roughness of the nickel plate wastaken as the surface roughness of the wire mesh. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. The arithmetic average roughnessRa was 0.64 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same mariner as in Example2-1, and the results are shown in Table 4.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 49.2 (mg/cm²). Thus, the result of evaluationof winding around column of 280 mm in diameter (2) was 88%, and theresult of evaluation of winding around column of 145 mm in diameter (3)was 42%. The portions at which the electrode came off from the membraneincreased. This is because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehandling property, which was evaluated as “3”. When the large sizeelectrode was actually operated, it was possible to evaluate thehandling property as “3”. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

Example 2-30

In Example 2-30, a nickel wire mesh having a gauge thickness of 200 μmand an opening ratio of 37% was used as the substrate for electrode forcathode electrolysis. A blast treatment was performed with alumina ofgrain-size number 320. The opening ratio was not changed after the blasttreatment. It is difficult to measure the surface roughness of the wiremesh. Thus, in Example 2-30, a nickel plate having a thickness of 1 mmwas simultaneously subjected to the blast treatment during the blasting,and the surface roughness of the nickel plate was taken as the surfaceroughness of the wire mesh. The arithmetic average roughness Ra was 0.65μm. The measurement of the surface roughness was performed under thesame conditions as for the surface roughness measurement of the nickelplate subjected to the blast treatment. Except for the above described,evaluation of electrode electrolysis, measurement results of theadhesive force, and adhesiveness were performed in the same manner as inExample 2-1. The results are shown in Table 4.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

The mass per unit area was 56.4 mg/cm². Thus, the result of evaluationmethod of winding around column of 145 mm in diameter (3) was 63%, andthe adhesiveness between the electrode and the membrane was poor. Thisis because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehand ting property, which was evaluated as “3”. The membrane damage wasevaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 19 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0096 (kPa·s/m) under the measurement condition 2.

Example 2-31

In Example 2-31, a full-roiled titanium expanded metal having a gaugethickness of 500 μm and an opening ratio of 17% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-31 atitanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blast ng, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.60 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 2-16, and the results are shown in Table4.

The thickness of the electrode was 508 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 152.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 μm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0072 (kPa·s/m) under the measurement condition 2.

Example 2-32

In Example 2-32, a full-rolled titanium expanded metal having a gaugethickness having 800 μm and an opening, ratio or 8% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-32, atitanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness or the wire mesh.The arithmetic average roughness Ra was 0.61 μm. The measurement of thesurface roughness m performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 2-16, and the results areshown in Table 4.

The thickness of the electrode was 808 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 251.3 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0172 (kPa·s/m) under the measurement condition 2.

Example 2-33

In Example 2-33, a full-rolled titanium expanded metal having a gaugethickness of 1000 μm and an opening ratio of 46% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 2-33, atitanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.59 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 2-16, and the results areshown in Table 4.

The thickness of the electrode was 1011 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 11 μm.

The mass per unit area was 245.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Example 2-34

A nickel line having a gauge thickness of 150 μm was provided as thesubstrate for electrode for cathode electrolysis. A roughening treatmentby this nickel line was performed. It is difficult to measure thesurface roughness of the nickel line. Thus, in Example 2-34, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the nickel line. Ablast treatment was performed with alumina of grain-size number 320. Thearithmetic average roughness Ra was 0.64 μm.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088 (tradename), thickness 10 mm) around a polyvinyl chloride (PVC) cylinder wasalways in contact with the above coating liquid. A coating roll aroundwhich the same EPDM had been wound was placed at the upper portionthereof, and a PVC roller was further placed thereabove. The coatingliquid was applied by allowing the substrate for electrode to passbetween the second coating roll and the PVC roller at the uppermostportion (roll coating method). Then, after drying at 50° C. for 10minutes, preliminary baking at 150° C. for 3 minutes, and baking at 350°C. for 10 minutes were performed. A series of these coating, drying,preliminary baking, and baking operations was repeated until apredetermined amount of coating was achieved. The thickness of onenickel line produced in Example 2-34 was 158 μm.

The nickel line produced by the above method was cut into a length of110 mm and a length of 95 mm. As shown in FIG. 37, the 110 mm nickelline and the 95 mm nickel line were placed such that the nickel linesvertically overlapped each other at the center of each of the nickellines and bonded to each other at the intersection with an instantadhesive (Aron Alpha(R), TOAGOSEI CO., LTD.) to produce an electrode.The electrode was evaluated, and the results are shown in Table 4.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.7%.

The mass per unit area of the electrode was 0.5 (1). The forces appliedper unit ma unit area (1) and (2) were both equal to or less than themeasurement lower limit of the tensile testing machine. Thus, the resultof evaluation of winding around column of 280 mm in diameter (1) wasless than 5%, and the portions at which the electrode came off from themembrane increased. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 15 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance value was 0.0002(kPa·s/m).

Additionally, the structure shown in FIG. 38 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.16 V.

Example 2-35

In Example 2-35, the electrode produced in Example 2-34 was used. Asshown in FIG. 39, the 110 mm nickel line and the 95 mm nickel line wereplaced such that the nickel lines vertically overlapped each other atthe center of each of the nickel lines and bonded to each other at theintersection with an instant adhesive (Aron Alpha(R), TOAGOSEI CO.,LTD.) to produce an electrode. The electrode was evaluated, and theresults are shown in Table 4.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.4%.

The mass per unit area of the electrode was 0.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 16 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0004 (kPa·s/m).

Additionally, the structure shown in FIG. 40 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

Example 2-36

In Example 2-36, the electrode produced in Example 2-34 was used. Asshown in FIG. 41, the 110 mm nickel line and the 95 mm nickel line wereplaced such that the nickel lines vertically overlapped each other atthe center of each of the nickel lines and bonded to each other at theintersection with an instant adhesive (Aron Alpha(R), TOAGOSEI CO.,LTD.) to produce an electrode. The electrode was evaluated, and theresults are shown in Table 4.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was98.8%.

The mass per unit area of the electrode was 1.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 14 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0005 (kPa·s/m).

Additionally, the structure shown in FIG. 42 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

Comparative Example 2-1

In Comparative Example 2-1, a thermal compressed assembly was producedby thermally compressing an electrode onto a membrane with reference toa prior art document (Examples of Japanese Patent Laid-Open No.58-48686).

A nickel expanded metal having a gauge thickness of 100 μm and anopening ratio of 33% was used as the substrate for electrode for cathodeelectrolysis to perform electrode coating in the same manner as inExample 2-1. Thereafter, one surface of the electrode was subjected toan inactivation treatment in the following procedure. Polyimide adhesiveape (Chukoh Chemical Industries, Ltd.) was attached to one surface ofthe electrode. A PTFE dispersion (Dupont-Mitsui Fluorochemicals Co.,Ltd., 31-JR (trade name) was applied onto the other surface and dried ina muffle furnace at 120° C. for 10 minutes. The polyimide tape waspeeled off, and a sintering treatment was performed in a muffle furnaceset at 380° C. for 10 minutes. This operation was repeated twice toinactivate the one surface of the electrode.

Produced was a membrane formed by two layers of a perfluorocarbonpolymer of which terminal functional group is “—COOCH₃” polymer) and aperfluorocarbon polymer of which terminal functional group is “—SO₂F” (Spolymer). The thickness of the C polymer layer was 3 mils, and thethickness of the S polymer layer was 4 mils. This two-layer membrane wassubjected to a saponification treatment to thereby introduce ionexchange groups to the terminals of the polymer by hydrolysis. The Cpolymer terminals were hydrolyzed into carboxylic groups and the Spolymer terminals into sulfo groups. The ion exchange capacity as thesulfonic acid group was 1.0 meq/g, and the ion exchange capacity as thecarboxylic acid group was 0.9 meq/g.

The inactivated electrode surface was oppositely disposed to andthermally pressed onto the surface having carboxylic acid groups as theion exchange groups to integrate the ion exchange membrane and theelectrode. The one surface of the electrode was exposed even after thethermal compression, and the electrode passed through no portion of themembrane.

Thereafter, in order to suppress attachment of bubbles to be generatedduring electrolysis to the membrane, a mixture of zirconium oxide and aperfluorocarbon polymer into which sulfo groups had been introduced wasapplied onto both the surfaces. Thus, the thermal compressed assembly ofComparative Example 2-1 was produced.

When the force applied per unit mass·unit area (1) was measured usingthis thermal compressed assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.50 (N/mg·cm²) was applied, aportion of the membrane was broken. The thermal compressed assembly ofComparative Example 2-1 had a force applied per unit mass·unit area (1)of at least 1.50 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed, the area in contact with the plastic pipe was less than 5%.Meanwhile, when evaluation of winding around column of 280 mm indiameter (2) was performed, the electrode and the membrane were 100%bonded to each other, but the membrane was not wound around the columnin the first place. The result of evaluation of winding around column of145 mm in diameter (3) was the same. The result meant that theintegrated electrode impaired the handling property of the membrane tothereby make it difficult to roll the membrane into a roll and fold themembrane. The handling property was “3”, which was problematic. Themembrane damage was evaluated as “0”. Additionally, when electrolyticevaluation was performed, the voltage was high, the current efficiencywas low, the common salt concentration in caustic soda (value convertedon the basis of 50%) was raised, and the electrolytic performancedeteriorated.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Comparative Example 2-2

In Comparative Example 2-2, a 40-mesh nickel mesh having a line diameterof 150 μm, a gauge thickness of 300 μm, and an opening ratio of 58% wasused as the substrate for electrode for cathode electrolysis. Except forthe above described, a thermal compressed assembly was produced in thesame manner as in Comparative Example 2-1.

When the force applied per unit mass·unit area (1) was measured usingthis thermal compressed assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.60 (N/mg·cm²) was applied, aportion of the membrane was broken. The thermal compressed assembly ofComparative Example 2-2 had a force applied per unit mass·unit area (1)of at least 1.60 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed using this thermal compressed assembly, the contact area withthe plastic pipe was less than 5%. Meanwhile, when evaluation of pipewas around column of 280 mm in diameter (2) was performed, the electrodeand the membrane were 100% bonded to each other, but the membrane wasnot wound around the column in the first place. The result of evaluationof winding around column of 145 mm (3) was the same. The result meantthat the integrated electrode impaired the handling property of themembrane to thereby make it difficult to roll the membrane into a rolland fold the membrane. The handling property was “3”, which wasproblematic. Additionally, when electrolytic evaluation was performed,the voltage was high, the current efficiency was low, the common saltconcentration in caustic soda was raised, and the electrolyticperformance deteriorated.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

TABLE 3 Substrate for Form of substrate Coating electrode for electrodemethod Feed conductor Example 2-1 Ni Punching Pyrolysis Ni mesh Example2-2 Ni Punching Pyrolysis Ni mesh Example 2-3 Ni Punching Pyrolysis Nimesh Example 2-4 Ni Punching Pyrolysis Ni mesh Example 2-5 Ni PunchingPyrolysis Ni mesh Example 2-6 Ni Punching Ion plating Ni mesh Example2-7 Ni Electroforming Pyrolysis Ni mesh Example 2-8 Ni ElectroformingPyrolysis Ni mesh Example 2-9 Ni Nonwoven fabric Pyrolysis Ni meshExample 2-10 Ni Nonwoven fabric Pyrolysis Ni mesh Example 2-11 Ni FoamedNi Pyrolysis Ni mesh Example 2-12 Ni Mesh Pyrolysis Ni mesh Example 2-13Ni Mesh Pyrolysis Ni mesh Example 2-14 Ni Punching (same PyrolysisMattress as in Example 2-3) Example 2-15 Ni Punching (same PyrolysisCathode having increase in voltage as in Example 2-3) Example 2-16 TiPunching Pyrolysis Anode having increase in voltage Example 2-17 TiPunching Pyrolysis Anode having increase in voltage Example 2-18 TiPunching Pyrolysis Anode having increase in voltage Example 2-19 TiPunching Pyrolysis Anode having increase in voltage Example 2-20 TiNonwoven fabric Pyrolysis Anode having increase in voltage Example 2-21Ti Mesh Pyrolysis Anode having increase in voltage Example 2-22 Ni/TiCombination of Pyrolysis Cathode and anode having increase in voltageExample 2-3 and Example 2-20 Example 2-23 Ni Punching Pyrolysis —Example 2-24 Carbon Woven fabric Pyrolysis Ni mesh Example 2-25 NiExpanded Pyrolysis Ni mesh Example 2-26 Ni Expanded Pyrolysis Ni meshExample 2-27 Ni Expanded Ion plating Ni mesh Example 2-28 Ni ExpandedPyrolysis Ni mesh Example 2-29 Ni Mesh Pyrolysis Ni mesh Example 2-30 NiMesh Pyrolysis Ni mesh Example 2-31 Ti Expanded Pyrolysis Anode havingincrease in voltage Example 2-32 Ti Expanded Pyrolysis Anode havingincrease in voltage Example 2-33 Ti Expanded Pyrolysis Anode havingincrease in voltage Example 2-34 Ni Mesh Pyrolysis Ni mesh Example 2-35Ni Mesh Pyrolysis Ni mesh Example 2-36 Ni Mesh Pyrolysis Ni meshComparative Ni Expanded Pyrolysis Ni mesh Example 2-1 Comparative NiMesh Pyrolysis Ni mesh Example 2-2

TABLE 4 Thickness of substrate for electrode for Thickness of ThicknessMass per Force applied per unit electrolysis electrode of catalyticOpening ratio unit area mass · unit area (1) (μm) (μm) layer (μm) (voidratio) % (mg/cm²) (N/mg · cm²-electrode) Example 2-1 16 24 8 49 5.8 0.90Example 2-2 22 29 7 44 9.9 0.61 Example 2-3 30 38 8 44 11.1 0.43 Example2-4 16 24 8 75 3.5 0.28 Example 2-5 20 30 10 49 6.4 0.59 Example 2-6 1626 10 49 6.2 0.81 Example 2-7 20 37 17 56 8.1 0.79 Example 2-8 50 60 1056 18.1 0.13 Example 2-9 150 165 15 76 31.9 0.22 Example 2-10 200 215 1572 46.3 0.12 Example 2-11 200 210 10 72 36.5 0.13 Example 2-12 100 11010 37 27.4 0.18 Example 2-13 130 133 3 38 36.3 0.15 Example 2-14 30 38 844 11.1 0.43 Example 2-15 30 38 8 44 11.1 0.43 Example 2-16 20 26 6 148.9 0.16 Example 2-17 20 30 10 30 8.1 0.26 Example 2-18 20 32 12 42 6.60.24 Example 2-19 50 69 19 47 12.9 0.12 Example 2-20 100 114 14 78 11.30.59 Example 2-21 120 140 20 42 14.9 0.47 Example 2-22 30/100 38/1148/14 44/78 11.1/11.3 0.43/0.59 Example 2-23 30 38 8 44 11.1 0.28 Example2-24 586 570 4 83 21.8 0.270 Example 2-25 100 114 14 33 67.5 0.05Example 2-26 100 107 7 16 78.1 0.04 Example 2-27 100 110 10 40 37.8 0.07Example 2-28 100 109 9 58 39.2 0.06 Example 2-29 300 308 8 56 49.2 0.18Example 2-30 200 210 10 37 56.4 0.09 Example 2-31 500 508 8 17 152.50.01 Example 2-32 800 808 8 8 251.3 0.01 Example 2-33 1000 1011 11 46245.5 0.01 Example 2-34 300 306 6 99.7 0.5 Equal to or less than themeasurement lower limit Example 2-35 300 306 6 99.4 0.9 Equal to or lessthan the measurement lower limit Example 2-36 300 306 6 98.8 1.9 Equalto or less than the measurement lower limit Comparative Example 2-1 100114 14 33 67.5 1.50 Comparative Example 2-2 300 308 8 58 49.2 1.60Method for Method for Method for evaluating evaluating evaluatingwinding winding winding around around around column of column of columnof 280 mm in 145 mm in 280 mm in diameter (2) diameter (3) diameter (1)(membrane (membrane Handing Force applied per unit (membrane and andproperty mass · unit area (2) and column) electrode) electrode) (sensory(N/mg · cm²-electrode) (%) (%) (%) evaluation) Example 2-1 0.640 100 100100 1 Example 2-2 0.235 100 100 100 1 Example 2-3 0.194 100 100 100 1Example 2-4 0.113 100 100 100 1 Example 2-5 0.386 100 100 100 1 Example2-6 0.650 100 100 100 1 Example 2-7 0.184 100 100 100 1 Example 2-80.088 100 100 100 1 Example 2-9 0.217 100 100 100 2 Example 2-10 0.081100 100 79 2 Example 2-11 0.162 100 100 100 2 Example 2-12 0.126 100 100100 1 Example 2-13 0.098 100 100 88 2 Example 2-14 0.194 100 100 100 1Example 2-15 0.194 100 100 100 1 Example 2-16 0.105 100 100 100 1Example 2-17 0.132 100 100 100 1 Example 2-18 0.147 100 100 100 1Example 2-19 0.08 100 100 100 1 Example 2-20 0.378 100 100 100 1 Example2-21 0.306 100 100 100 1 Example 2-22 0.194/0.378 100/100 100/100100/100 1/1 Example 2-23 0.194 100 100 100 1 Example 2-24 0.3 100 100100 2 Example 2-25 0.045 100 64 22 4 Example 2-26 0.027 100 37 25 4Example 2-27 0.045 100 80 32 3 Example 2-28 0.034 100 69 39 3 Example2-29 0.138 100 88 42 3 Example 2-30 0.060 100 100 63 3 Example 2-310.005 100 Less than 5 Less than 5 4 Example 2-32 0.006 100 Less than 5Less than 5 4 Example 2-33 0.005 100 Less than 5 Less than 5 4 Example2-34 Equal to or less than the Less than 5 — — 4 measurement lower limitExample 2-35 Equal to or less than the Less than 5 — — 4 measurementlower limit Example 2-36 Equal to or less than the Less than 5 — — 4measurement lower limit Comparative Example 2-1 — Less than 5 — — 3Comparative Example 2-2 — Less than 5 — — 3 Elastic deformation test ofelectrode Electrolytic evaluation (winding around Common salt vinylchloride Ventilation Ventilation concentration pipe of 32 mm inresistance resistance Current in caustic soda outer diameter) (KPa ·s/m) (KPa · s/m) Membrane Voltage efficiency (ppm, on the average valueof (measurement (measurement damage (V) (%) basis of 50%) L₁ and L₂ (mm)condition 1) condition 2) evaluation Example 2-1 2.98 97.7 15 0 0.07 orless 0.0028 0 Example 2-2 2.95 97.2 18 0 0.07 or less 0.0033 0 Example2-3 2.96 97.6 19 0 0.07 or less 0.0027 0 Example 2-4 2.97 97.5 15 0 0.07or less 0.0023 0 Example 2-5 2.95 97.1 18 0 0.07 or less 0.0023 0Example 2-6 2.96 97.3 14 0 0.07 or less 0.0028 0 Example 2-7 2.96 97.315 0 0.07 or less 0.0032 0 Example 2-8 2.96 97.7 16 0 0.07 or less0.0032 0 Example 2-9 2.97 96.8 23 29 0.07 or less 0.0612 0 Example 2-102.96 96.7 26 40 0.07 or less 0.0164 0 Example 2-11 3.05 97.4 22 17 0.07or less 0.0402 0 Example 2-12 3.11 97.2 23 0.5 0.07 or less 0.0154 0Example 2-13 3.09 97.0 25 6.5 0.07 or less 0.0124 0 Example 2-14 2.9797.3 18 0 0.07 or less 0.0027 0 Example 2-15 2.96 97.2 21 0 0.07 or less0.0027 0 Example 2-16 3.10 96.8 19 4 0.07 or less 0.0060 0 Example 2-173.07 96.8 26 5 0.07 or less 0.0030 0 Example 2-18 3.08 97.7 21 2.5 0.07or less 0.0022 0 Example 2-19 3.09 97.0 21 8 0.07 or less 0.0024 0Example 2-20 2.97 96.8 24 2 0.07 or less 0.0228 0 Example 2-21 2.99 97.018 10 0.07 or less 0.0132 0 Example 2-22 3.00 97.2 17 0/2 0.07 or less0.0027/0.0228 0 Example 2-23 — — — 0 0.07 or less 0.0027 — Example 2-243.19 97.0 20 0 0.19 0.176 1 Example 2-25 2.98 97.7 19 13 0.07 or less0.0168 0 Example 2-26 2.99 97.8 17 18.5 0.07 or less 0.0176 0 Example2-27 2.96 97.5 18 11 0.07 or less 0.0030 0 Example 2-28 2.99 97.6 1811.5 0.07 or less 0.0028 0 Example 2-29 2.95 97.5 24 23 0.07 or less0.0034 0 Example 2-30 2.98 97.3 23 19 0.07 or less 0.0096 0 Example 2-312.99 96.7 23 Remained 0.07 or less 0.0072 0 Example 2-32 3.02 97.0 19deformed in vinyl 0.07 or less 0.0172 0 Example 2-33 3.00 97.2 20chloride form and 0.07 or less 0.0027 0 did not return Example 2-34 3.1697.5 21 15 0.07 or less 0.0002 0 Example 2-35 3.18 97.4 19 16 0.07 orless 0.0004 0 Example 2-36 3.18 97.3 20 14 0.07 or less 0.0005 0Comparative Example 2-1 3.67 93.8 226 13 0.07 or less 0.0168 0Comparative Example 2-2 3.71 94.5 155 23 0.07 or less 0.0034 0

In Table 4, all the samples were able to stand by themselves by thesurface tension before measurement of “force applied per unit mass·unitarea (1)” and “force applied per unit mass·unit area (2)” (i.e., did notslip down).

<Verification of Third Embodiment>

As will be described below, Experiment Examples according to the thirdembodiment (in the section of <Verification of third embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the third embodiment (in the section of <Verificationof third embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 57 to 62 asappropriate.

(1) Electrolytic Evaluation (Voltage (V), Current Efficiency (?))

The electrolytic performance was evaluated by the following electrolyticexperiment.

A titanium anode cell having an anode chamber in which an anode wasprovided (anode terminal cell) and a cathode cell having a nickelcathode chamber in which a cathode was provided (cathode terminal cell)were oppositely disposed. A pair of gaskets was arranged between thecells, and an ion exchange membrane was sandwiched between the gaskets.Then, the anode cell, the gasket, the ion exchange membrane, the gasket,and the cathode were brought into close contact together to obtain anelectrolytic cell.

The anode was produced by applying a mixed solution of rutheniumchloride, iridium chloride, and titanium tetrachloride onto a titaniumsubstrate subjected to blasting and acid etching treatment as thepretreatment, followed by drying and baking. The anode was fixed in theanode chamber by welding. As the cathode, one described in each ofExamples and Comparative Examples was used. As the collector of thecathode chamber, a nickel expanded metal was used. The collector had asize of 95 mm in length×110 mm in width. As a metal elastic body, amattress formed by knitting nickel fine wire was used. The mattress asthe metal elastic body was placed on the collector. Nickel mesh formedby plain-weaving nickel wire having a diameter of 150 μm in a sieve meshsize of 40 was placed thereover, and a string made of Teflon(R) was usedto fix the four corners of the Ni mesh to the collector. This Ni meshwas used as a feed conductor. In this electrolytic cell, the repulsiveforce of the mattress as the metal elastic body was used so as toachieve a zero-gap structure. As the gaskets, ethylene propylene diene(EPDM) rubber gaskets were used. As the membrane, an ion exchangemembrane below was used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluorinethylene (PTEF) were used (hereinafter referred to asPTFE yarns). As the sacrifice yarns, yarns obtained by twisting six 3.5denier filaments of polyethylene terephthalate (PET) 200 times/m wereused. First, in each of the ID and the MD, the PTFE yarns and thesacrifice yarns re plain-woven with 24 PTFE yarns/inch so that twosacrifice yarns were arranged between adjacent PTFE yarns, to obtain awoven fabric. The resulting woven fabric was pressure-bonded by a rollto obtain a woven fabric having a thickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin B of a dry resin that was a copolymer ofCF₂═F₂ and CF₂═CFOCF₂CF(CF₂)OCF₂CF₂SO₂F and had an ion exchange capacityof 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for 1 hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Further, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having an average particle size(primary particle size) of 1 μm was added to a 5% by mass ethanolsolution of the acid-type resin of the resin B and dispersed to preparea suspension, and the suspension was sprayed onto both the surfaces ofthe above composite membrane by a suspension spray method to formcoatings of zirconium oxide on the surfaces of the composite membrane toobtain an ion exchange membrane. The coating density of zirconium oxidemeasured by fluorescent X-ray measurement was 0.5 mg/cm². The averageparticle size was measured by a particle size analyzer (e.g.,manufactured by SHIMADZU CORPORATION, “SALD(R) 2200”).

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted such that the temperature in each electrolytic cell reached 90°C. Common salt electrolysis was performed at a current density of 6kA/m² to measure the voltage and current density. The current efficiencyhere is the proportion of the amount of the produced caustic soda to thepassed current, and when impurity ions and hydroxide ions rather thansodium ions move through the ion exchange membrane due to the passedcurrent, the current efficiency decreases. The current efficiency wasobtained by dividing the number of moles of caustic soda produced for acertain time period by the number of moles of the electrons of thecurrent passing during that time period. The number of moles of causticsoda was obtained by recovering caustic soda produced by theelectrolysis in a plastic container and measuring its mass.

(2) Handling Property (Response Evaluation)

(A) The ion exchange membrane (membrane) mentioned above was cut into a170 mm square, and the electrode obtained each of Examples andComparative Examples mentioned below was cut into a size of 95×110 mm.The ion exchange membrane and the electrode were laminated and placedstill on a Teflon plate. The interval between the anode cell and thecathode cell used in the electrolytic evaluation was set at about 3 cm.The laminate placed still was lifted, and an operation of inserting andholding the laminate therebetween was conducted. This operation wasconducted while the electrode was checked for dislocation and dropping.

(B) The laminate was placed still on a Teflon plate in the same manneras in the above (A). The adjacent two corners of the membrane portion ofthe laminate were held by hands to lift the laminate so as to bevertical. The two corners held by hands were moved from this state to beclose to each other such that the membrane was protruded or recessed.This operation was repeated again to check the conformability of theelectrode to the membrane. The results were evaluated on a four levelscale of 1 to 4 on the basis of the following indices:

1: good handling property

2: capable of being handled

3: difficult to handle

4: substantially incapable of being handled

Here, with respect to the samples of Examples 3-4 and 3-6, sampleshaving the same size as that of the large electrolytic cell were alsosubjected to handling property evaluation, as mentioned below. Theevaluation results of Example 3-4 and 3-6 were used as indices toevaluate the difference between the evaluation of the above (A) and (B)and that of the large-sized ones. That is, in the case where theevaluation result of a small laminate was “1” or “2”, it was judged thatthe handling property becomes good even if the laminate was provided ina larger size.

(3) Proportion of Fixed Region

The area of the surface opposed to the electrode for electrolysis in theion exchange membrane (the total of the portion corresponding to theconducting surface and the portion corresponding to non-conductingsurface) was calculated as an area S1. Next, the area of the electrodefor electrolysis was calculated as an area of the conducting surface S2.The areas S1 and S2 were identified with the area of the laminate of theion exchange membrane and electrode for electrolysis when viewed fromthe side of the electrode for electrolysis (see FIG. 57). With respectto the shape of the electrode for electrolysis, even an electrode havingopenings had an opening ratio of less than 90%. Thus, the electrode forelectrolysis was considered a flat plate (the opening portion was to beincluded in the area).

The area of the fixed region S3 was also identified as the area en thelaminate was viewed from the top as in FIG. 57 (the same applies to thearea of the portion only corresponding to the conducting surface S3′).In the case where PTFE tape mentioned below was fixed as a fixingmember, the overlapping portion of the tape was not to be included inthe area. Alternatively, in the case where PTFE yarns and an adhesivementioned below were fixed as fixing members, the area present on theback sides of the electrode and the membrane was included into the area.

As described above, 100×(S3/S1) was calculated as the proportion of thearea of fixed region α (%) relative to the area of the surface opposedto the electrode for electrolysis in the ion exchange membrane.Additionally, 100×S3′/S2 was calculated as the proportion of the area ofthe portion only corresponding to the conducting surface of the fixedregion β relative to the area of the conducting surface.

Example 3-1

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 22 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.96 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching The opening ratio was 44%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure ruthenium nitrate solution having a rutheniumconcentration of 100 g/L (FURUYA METAL Co., Ltd.) and cerium nitrate(KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molar ratiobetween the ruthenium element and the cerium element was 1:0.25. Thismixed solution was sufficiently stirred and used as a cathode coatingliquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced in Example 3-1 was 24μm. The thickness of the catalytic layer containing ruthenium oxide andcerium oxide, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm. The coating was formed also on the surface notroughened.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The roughenedsurface of the electrode was oppositely disposed on a substantial centerposition of the carboxylic acid layer side of the ion exchange membrane(size: 160 mm×160 mm) equilibrated with a 0.1 N NaOH aqueous solution.PTFE tape (manufactured by NITTO DENKO CORPORATION) was used to fix thefour sides such that the ion exchange membrane and the electrode weresandwiched as shown in FIG. 57 (note that FIG. 57 illustrates aschematic view for illustrative purposes only, and the dimensions arenot necessarily accurate. The same applies to the following figures). InExample 3-1, the PTFE tape was the fixing member, the proportion α was60%, and the proportion β was 1.0%.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The above membrane-integrated electrode was sandwiched between the anodecell and the cathode cell such that the surface onto which the electrodewas attached was allowed to face the cathode chamber side. In thesectional structure, the collector, the mattress, the nickel mesh feedconductor, the electrode, the membrane, and the anode are arranged inthis order from the cathode chamber side to form a zero-gap structure.

The resulting electrode was subjected to evaluation. The results areshown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also relatively good: “2”.

Example 3-2

Evaluation was performed in the same manner as in Example 3-1 except forincreasing the area at which the PTFE tape overlapped the electrolyticsurface as shown in FIG. 58. That is, in Example 3-2, the area of thePTFE tape was allowed to increase in the in-plane direction of theelectrode for electrolysis, and thus, the area of the electrolyticsurface in the electrode for electrolysis decreased than in Example 3-1.In Example 3-2, the proportion α was 69%, and the proportion β was 23%.The evaluation results are shown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also good: “1”.

Example 3-3

Evaluation was performed in the same manner as in Example 3-1 except forincreasing the area at which the PTFE tape overlapped the electrolyticsurface as shown in FIG. 59. That is, in Example 3-3, the area of thePTFE tape was allowed to increase in the in-plane direction of theelectrode for electrolysis, and thus, the area of the electrolyticsurface in the electrode for electrolysis decreased than in Example 3-1.In Example the proportion α was 87%, and the proportion β was 67%. Theevaluation results are shown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also good: “1”.

Example 3-4

An electrode identical to that of Example 3-1 was provided and cut intoa size of 95 mm in length and 110 mm in width for electrolyticevaluation. The roughened surface of the electrode was oppositelydisposed on a substantial center position of the carboxylic acid layerside of the ion exchange membrane (size: 160 mm×160 mm) equilibratedwith a 0.1 N NaOH aqueous solution. PTFE yarn was used to sew theelectrode at the lea side thereof in a vertical direction onto the ionexchange membrane, as shown in FIG. 60. The PTFE yarn was allowed topass through a portion at a vertical distance of 10 mm and a horizontaldistance of 10 mm from a corner of the electrode, from the back side ofthe sheet of FIG. 60 to the front side thereof, allowed to pass througha portion at a vertical distance of 35 mm and a horizontal distance of10 mm, from the front side of the sheet to the back side, allowed topass through a portion at a vertical distance of 60 mm and a horizontaldistance of 10 mm, again from the back side of the sheet to the frontside thereof, and allowed to pass through a portion at a verticaldistance of 85 mm and a horizontal distance of 10 mm, from the frontside of the sheet to the back side thereof. A solution obtaineddispersing an acid-type resin S of a resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₂)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g at a content of 5% mass in ethanol wasapplied onto the portions at which the yarn passed through the ionexchange membrane.

As described above, in Example the proportion α was 0.35%, and theproportion β was 0.86%.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode face the ground side, the electrode did not falloff. Even when both the ends of one side were pinched and hung such thatthe membrane-integrated electrode was vertical to the ground, theelectrode did not all off.

The resulting electrode was subjected to evaluation. The results areshown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also relatively good: “2”.

Additionally, an ion exchange membrane and an electrode each formed in alarger size were provided in Example 3-4. An ion exchange membranehaving a size of 1.5 m in length and 2.5 m in width and four cathodeshaving a size of 0.3 m in length and 2.4 m in width were provided. Thecathodes were arranged without any gap on the carboxylic acid layer sideof the ion exchange membrane, and the cathodes were bonded to the ionexchange membrane by PTFE yarn to produce a laminate. In this Example,the proportion α was 0.013%, and the proportion β was 0.017%.

When an operation of fitting a large electrolyzer with themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, was performed, it was possible to achievesmooth fitting.

Example 3-5

An electrode identical to that of Example 3-1 was provided and cut intoa size of 95 mm in length and 110 mm in width for electrolyticevaluation. The roughened surface of the electrode was oppositelydisposed on a substantial center position of the carboxylic acid layerside of the ion exchange membrane (size: 160 mm×160 mm) equilibratedwith a 0.1 N NaOH aqueous solution. A fixing resin mad of polypropyleneshown in FIG. 61 was used to fix the ion exchange membrane and theelectrode. That is, the resin was placed at two portions in total: aportion at a vertical distance of 20 mm and a horizontal distance of 20mm from a corner of the electrode, and additionally, a portion at avertical distance of 20 mm and a horizontal distance of 20 mm from thecorner located therebelow. Onto the portions at which the fixing resinpassed through the ion exchange membrane, a solution similar to that ofExample 3-4 was applied.

As described above, in Example 3-5, the fixing resin and the resin Sserved as fixing members, the proportion α was 0.47%, and the proportionβ was 1.1%.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground allowingthe electrode to face the ground side, the electrode did not fall off.Even when both ends of one side were pinched and hung such that themembrane-integrated electrode was vertical to the ground, the electrodedid not fall off.

The resulting electrode was subjected to evaluation. The results areshown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also relatively good: “2”.

Example 3-6

An electrode identical to that of Example 3-1 was provided and cut intoa size of 95 mm in length and 110 mm in width for electrolyticevaluation. The roughened surface of the electrode was oppositelydisposed on a substantial center position of the carboxylic acid layerside of the ion exchange membrane (size: 160 mm×160 mm) equilibratedwith a 0.1 N NaOH aqueous solution. As shown in FIG. 62, a cyanoacrylateadhesive (trade name: Aron Alpha, TOAGOSEI CO., LTD.) was used to fixthe ion exchange membrane and the electrode. That is, the membrane andthe electrode were fixed with the adhesive at five points on a verticalside of the electrode (the points were each equally spaced) and eightpoints on a horizontal side of the electrode (the points were eachequally spaced).

As described above, in Example 3-6, the adhesive served as fixingmembers, the proportion α of 0.78%, and the proportion β was 1.9%.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notfail off. Even when both the ends of one side were pinched and hung suchthat the membrane-integrated electrode was vertical to the ground, theelectrode did not fall off.

The resulting electrode was subjected to evaluation. The results areshown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also relatively good: “1”.

Additionally, an ion exchange membrane and an electrode each formed in alarger size were provided in Example 3-6. An ion exchange membranehaving a size of 1.5 m in length and 2.5 m in width and four cathodeshaving a size of 0.3 m in length and 2.4 m in width were provided. Theedge of one horizontal side of each four cathodes was connected to eachother with the adhesive above to form one large cathode (1.2 m in lengthand 2.4 m in width). This large cathode was bonded to the center portionon the carboxylic acid layer side of the ion exchange membrane with AronAlpha to produce a laminate. That is, the membrane and the electrodewere fixed with the adhesive at five points on a vertical side of theelectrode (the points were each equally spaced) and eight points on ahorizontal side of the electrode (the points were each equally spaced),in the same manner as in FIG. 62. In this Example, the proportion α was0.019%, and the proportion β was 0.024%.

When an operation of fitting a large electrolyzer with themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, was performed, it was possible to achievesmooth fitting.

Example 3-7

An electrode identical to that of Example 3-1 was provided and cut intoa size of 95 mm in length and 110 mm in width for electrolyticevaluation. The roughened surface of the electrode was oppositelydisposed on a substantial center position of the carboxylic acid layerside of the ion exchange membrane (size: 160 mm×160 mm) equilibratedwith a 0.1 N NaOH aqueous solution. A solution similar to that ofExample 3-4 was applied to fix the ion exchange membrane and theelectrode. That is, the resin was placed at two portions in total: aportion at a vertical distance of 20 mm and a horizontal distance of 20mm from a corner of the electrode, and additionally, a portion at avertical distance of 20 mm and a horizontal distance of 20 mm from thecorner located therebelow (see FIG. 61).

As described above, in Example 3-7, the resin S served as fixingmembers, the proportion α was 2.0%, and the proportion β was 4.8%.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notfall off. Even when both the ends of one side were pinched and hung suchthat the membrane-integrated electrode was vertical to the ground, theelectrode did not fall off.

The resulting electrode was subjected to evaluation. The results areshown in Table 5.

The electrode exhibited a low voltage and high current efficiency. Thehandling property was also relatively good: “2”.

Comparative Example 3-1

Evaluation was performed in the same manner as in Example 3-1 except forincreasing the area at which the PTFE tape overlapped the electrolyticsurface. That is, in Comparative Example 3-1, the area of the PTFE tapewas allowed to increase in the in-plane direction of the electrode forelectrolysis, and thus, the area of the electrolytic surface in theelectrode for electrolysis decreased than in Example 3-1. In ComparativeExample 3-1, the proportion α is 93%, and the proportion β is 83%. Theevaluation results are shown in Table 5.

The voltage was high, and the current efficiency was also low. Thehandling property was good: “1”.

Comparative Example 3-2

Evaluation was performed in the same manner as in Example 3-1 except forincreasing the area at which the PTFE tape overlapped the electrolyticsurface. The evaluation results are shown in Table 5. That is, inComparative Example 3-2, the area of the PTFE tape was allowed toincrease in the in-plane direction of the electrode for electrolysis.

In Comparative Example 3-2, the proportion α and the proportion β were100%, and the entire electrolytic surface was a fixed region coveredwith PTFE. Accordingly, it was not possible to supply an electrolytesolution, and thus, it was not possible to perform electrolysis. Thehandling property was good: “1”.

Comparative Example 3-3

Evaluation was performed in the same manner as in Example 3-1 except noPTFE tape was used, that is, the proportion α and the proportion β were0%. The evaluation results are shown in Table 5.

The electrode exhibited a low voltage and high current efficiency.Meanwhile, since there were no fixed region of the membrane and theelectrode, it was not possible to handle the membrane and the electrodeas a laminate (integrated piece), and thus, the handling property was“4”.

The evaluation results of Examples 3-1 to 7 and Comparative Examples 3-1to 3 were also shown in Table 5 below.

TABLE 5 Area of Area of fixed region Electrolytic substrate for Areacorresponding Handling evaluation Area of electrode for of fixed only toProportion α Proportion β property Current membrane electrolysis regionconducting surface 100 * S3/S1 100 * S3′/S2 (sensory Voltage efficiencyS1 S2 S3 S3′ (%) (%) evaluation) (V) (%) Example 3-1 256 104.5 153 1.060 1.0 2 2.98 97.8 Example 3-2 256 104.5 176 24 69 23 1 3.11 97.7Example 3-3 256 104.5 222 70 87 67 1 3.85 96.1 Example 3-4 256 104.50.90 0.90 0.35 0.86 2 2.99 92.2 Example 3-5 256 104.5 1.2 1.2 0.47 1.1 23.00 92.5 Example 3-8 256 104.5 2.0 2.0 0.78 1.9 2 2.97 97.5 Example 3-7256 104.5 5.0 5.0 2.0 4.8 2 2.99 97.0 Comparative Example 3-1 256 104.5239 87 93 83 1 5.50 86.8 Comparative Example 3-2 258 104.5 256 104.5 100100 1 Impossible to electrolyze Comparative Example 3-3 256 104.5 0 0 00 4 2.97 97.5

<Verification of Fourth Embodiment>

As will be described below, Experiment Examples according to the fourthembodiment (in the section of <Verification of fourth embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the fourth embodiment (in the section of <Verificationof fourth embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 79 to 90 asappropriate.

[Evaluation Method] (1) Opening Ratio

An electrode was cut into a size of 130 mm×100 mm. A digimatic thicknessgauge (manufactured by Mitutoyo Corporation, minimum scale 0.001 mm) wasused to calculate an average value of 10 points obtained by measuringevenly in the plane. The value was used as the thickness of theelectrode (gauge thickness) to calculate the volume. Thereafter, anelectronic balance was used to measure the mass. From the specificgravity of each metal (specific gravity of nickel=8.908 g/cm³, specificgravity of titanium=4.506 g/cm³), the opening ratio or void ratio wascalculated.

Opening ratio (Void ratio) (%)=(1−(electrode mass)/(electrodevolume×metal specific gravity))×100

(2) Mass per Unit Area (mg/cm²)

An electrode was cut into a size of 130 mm×100 mm, and the mass thereofwas measured by an electronic balance. The value was divided by the area(130 mm×100 mm) to calculate the mass per unit area.

(3) Force Applied per Unit Mass·Unit Area (1) (Adhesive Force)(N/mg·cm²))

[Method (i)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-6001 type load cell).

A 200 mm square nickel plate having a thickness of 1.2 mm was subjectedto blast processing with alumina of grain-size number 320. Thearithmetic average surface roughness (Ra) of the nickel plate after theblast treatment was 0.7 μm. For surface roughness measurement herein, aprobe type surface roughness measurement instrument SJ-310 (MitutoyoCorporation) was used. A measurement sample was placed on the surfaceplate parallel to the ground surface to measure the arithmetic averageroughness Ra under measurement conditions as described below. Themeasurement was repeated 6 times, and the average value was listed.

<Probe shape> conical taper angle=60°, tip radius=2 μm, static measuringforce=0.75 mN

<Roughness standard> JIS2001

<Evaluation curve> R

<Filter> GAUSS

<Cutoff value λc> 0.8 mm

<Cutoff value λs> 2.5 μm

<Number of sections> 5

<Pre-running, post-running> available

This nickel plate was vertically fixed on the lower chuck of the tensileand compression testing machine.

As the membrane, an ion exchange membrane A below was used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTFE) were used (hereinafter referred to asPTFE yarns). As sacrifice yarns, yarns obtained by twisting six 35denier filaments of polyethylene terephthalate (PET) 200 times/m wereused (hereinafter referred to as PET yarns). First, in each of the TDand the MD, the PTFE yarns and the sacrifice yarns were plain-woven with24 PTFE yarns/inch so that two sacrifice yarns were arranged betweenadjacent PTFE yarns, to obtain a woven fabric. The resulting wovenfabric was pressure-bonded by a roll to obtain a woven fabric having athickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin b or a dry resin that was a copolymer orCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% oymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried 60° C.

Further, 20% by mass of rconium oxide having a primary particle size of1 μm was added to a 5% by mass ethanol solution of the acid-type resinof the resin B and dispersed to prepare a suspension, and the suspensionwas sprayed onto both the surfaces of the above composite membrane by asuspension spray method to form coatings of zirconium oxide on thesurfaces of the composite membrane to obtain an ion exchange membrane A.The coating density of zirconium oxide measured by fluorescent X-raymeasurement was 0.5 mg/cm². The average particle size was measured by apartcle size analyzer (manufactured by SHIMADZU CORPORATION, “SALD(R)2200”).

The ion exchange membrane (membrane) obtained above was immersed in purewater for 12 hours or more and then used for the test. The membrane wasbrought into contact with the above plate sufficiently moistened withpure water and allowed to adhere to the plate by the tension of water.At this time, the nickel plate and the ion exchange membrane were placedso as to align the upper ends thereof.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedby the upper chuck of the tensile and compression testing machine tohang the electrode. The load applied on the testing machine at this timewas set to 0 N. The integrated piece of the stainless plates, electrode,and clips was once removed from the tensile and compression testingmachine, and immersed in a vat containing pure water in order to moistenthe electrode sufficiently with pure water. Thereafter, the center ofthe stainless plates was clamped again by the upper chuck of the tensileand compression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the ion exchange membrane by the surfacetension of pure water. The size of the adhesive surface at this time was130 mm in width and 110 mm in length. Pure water in a wash bottle wassprayed to the electrode and the ion exchange membrane entirely so as tosufficiently moisten the membrane and the electrode again. Thereafter, aroller formed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess pure water. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the overlapping portion ofthe electrode and the membrane reached 130 mm in width and 100 mm inlength was recorded. The measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion ofthe electrode and the ion exchange membrane and the mass of theelectrode of the portion overlapping the ion exchange membrane tocalculate the force applied per unit mass·unit area (1). The mass of theelectrode of the portion overlapping the ion exchange membrane wasdetermined through proportional calculation from the value obtained in(2) Mass per unit area (mg/cm²) described above.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to the ion exchange membrane that adhered to avertically-fixed nickel plate via the surface tension.

A schematic view of a method for evaluating the force applied (1) isshown in. FIG. 79.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(4) Force Applied per Unit Mass·Unit Area (2) (Adhesive Force)(N/mg·cm²))

[Method (ii)]

A tensile and compression testing machine was used for measurement(Imada-SS Corporation, main testing machine: SDT-52NA type tensile andcompression testing machine, load cell: SL-600 type load cell).

A nickel plate identical to that in Method (i) was vertically fixed onthe lower chuck of the tensile and compression testing machine.

A sample of electrode for electrolysis (electrode) to be used formeasurement was cut into a 130 mm square. The ion exchange membrane Awas cut into a 170 mm square. One side of the electrode was sandwichedby two stainless plates (thickness: 1 mm, length: 9 mm, width: 170 mm).After positioning so as to align the center of the stainless plates withthe center of the electrode, four clips were used for uniformly fixingthe electrode and plates. The center of the stainless plates was clampedby the upper chuck of the tensile and compression testing machine tohang the electrode. The load applied on the testing machine at this timewas set to 0 N. The integrated piece of the stainless plates, electrode,and claps was once removed from the tensile and compression testingmachine, and immersed in a vat containing pure water in order to moistenthe electrode sufficiently with pure water. Thereafter, the center ofthe stainless plates was clamped again by the upper chuck of the tensileand compression testing machine to hang the electrode.

The upper chuck of the tensile and compression testing machine waslowered, and the sample of electrode for electrolysis was allowed toadhere to the surface of the nickel plate via the surface tension of asolution. The size of the adhesive surface at this time was 130 mm inwidth and 110 mm in length. Pure water in a wash bottle was sprayed tothe electrode and the nickel plate entirely so as to sufficientlymoisten the nickel plate and the electrode again. Thereafter, a rollerformed by winding a closed-cell type EPDM sponge rubber having athickness of 5 mm around a vinyl chloride pipe (outer diameter: 38 mm)was rolled downward from above with lightly pressed over the electrodeto remove excess solution. The roller was rolled only once.

The electrode was raised at a rate of 10 mm/minute to begin loadmeasurement, and the load when the size of the over portion of theelectrode and the nickel plate in the longitudinal direction reached 100mm was recorded. This measurement was repeated three times, and theaverage value was calculated.

This average value was divided by the area of the overlapping portion orthe electrode and the nickel plate and the mass of the electrode of theportion overlapping the nickel plate to calculate the force applied perunit mass·unit area (2). The mass of the electrode of the portionoverlapping the membrane was determined through proportional calculationfrom the value obtained in Mass per unit area (mg/cm²) described above.

As for the environment of the measuring chamber, the temperature was23±2° C. and the relative humidity was

The electrode used in Examples and Comparative Examples was able tostand by itself and adhere without slipping down or coming off whenallowed to adhere to a vertically-fixed nickel plate via the surfacetension.

The measurement lower limit of the tensile testing machine was 0.01 (N).

(5) Method for Evaluating Winding Around Column of 280 mm in Diameter(1) (%) (Membrane and Column)

The evaluation method (1) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square. The ion exchange membrane was immersed in purewater for 12 hours or more and then used for the test. In Examples 33and 34, the electrode had been integrated with the ion exchange membraneby thermal pressing, and thus, an integrated piece of an ion exchangemembrane and an electrode was provided (electrode of a 130 mm square).After the ion exchange membrane was sufficiently immersed in pure water,the membrane was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 280 mm. Thereafter,excess solution was removed with a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm). The roller was rolled overthe ion exchange membrane from the left to the right of the schematicview shown in FIG. 80. The roller was rolled only once. One minuteafter, the proportion of a portion at which the ion exchange membranewas brought into a close contact with the plastic pipe electrode havingan outer diameter of 280 mm was measured.

(6) Method for Evaluating Winding Around Column of 280 mm in Diameter(2) (%) (Membrane and Electrode)

The evaluation method (2) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 man square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 280 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 81 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(7) Method for Evaluating Winding Around Column of 145 mm in Diameter(3) (%) (Membrane and Electrode)

The evaluation method (3) was conducted by the following procedure.

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a 130 mm square.The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. The ion exchange membrane and theelectrode were sufficiently immersed in pure water and then laminated.This laminate was placed on the curved surface of a plastic(polyethylene) pipe having an outer diameter of 145 mm such that theelectrode was located outside. Thereafter, a roller formed by winding aclosed-cell type EPDM sponge rubber having a thickness of 5 mm around avinyl chloride pipe (outer diameter: 38 mm) was rolled from the left tothe right of the schematic view shown in FIG. 82 with lightly pressedover the electrode to remove excess solution. The roller was rolled onlyonce. One minute after, the proportion of a portion at which the ionexchange membrane was brought into a close contact with the electrodewas measured.

(8) Handling Property (Response Evaluation)

The ion exchange membrane A (membrane) produced in [Method (i)] was cutinto a 170 mm square, and the electrode was cut into a size of 95×110mm. The ion exchange membrane was immersed in pure water for 12 hours ormore and then used for the test. In each Example, the ion exchangemembrane and electrode were sufficiently immersed in three solutions:sodium bicarbonate aqueous solution, 0.1N NaOH aqueous solution, andpure water, then laminated, and placed still or a Teflon plate. Theinterval between the anode cell and the cathode cell used in theelectrolytic evaluation was set at about 3 cm. The laminate placed stillwas lifted, and an operation of inserting and holding the laminatetherebetween was conducted. This operation am conducted while theelectrode was checked for dislocation and dropping.

(B) The ion exchange membrane A (membrane) produced in [Method (i)] wascut into a 170 mm square, and the electrode was cut into a size of95×110 mm. The ion exchange membrane was immersed in pure water for 12hours or more and then used for the test. In each Example, the ionexchange membrane and electrode were sufficiently immersed in threesolutions: a sodium bicarbonate aqueous solution, a 0.1N NaOH aqueoussolution, and pure water, then laminated, and placed still on a Teflonplate. The adjacent two corners of the membrane portion of the laminatewere held by hands to lift the laminate so as to be vertical. The twocorners held by hands were moved from this state to be close to eachother such that the membrane was protruded or recessed. This move wasrepeated again to check the conformability of the electrode to themembrane. The results were evaluated on a four level scale of 1 to 4 onthe basis of the following indices:

1: good handling property

2: capable of being handled

3: difficult to handle

4: substantially incapable of being handled

Here, the sample of Example 4-28, provided in a size equivalent to thatof a large electrolytic cell including an electrode in a size of 1.3m×2.5 m and an ion exchange membrane in a size of 1.5 m×2.8 m, was,subjected to handling. The evaluation result of Example (“3” asdescribed below) was used as an index to evaluate the difference betweenthe evaluation of the above (A) and (B) and that of the large-sized one.That is, in the case where the evaluation result of a small laminate was“1” or “2”, it was judged that there was no problem in the handlingproperty even if the laminate was provided in a larger size.

(9) Electrolytic Evaluation (Voltage (V), Current Efficiency (%), CommonSalt Concentration in Caustic Soda (ppm, on the Basis of 50%))

The electrolytic performance was evaluated by the following electrolyticexperiment.

A titanium anode cell having an anode chamber in which an anode wasprovided (anode terminal cell) and a cathode cell having a nickelcathode chamber in which a cathode was provided (cathode terminal cell)were oppositely disposed. A pair of gaskets was arranged between thecells, and a laminate (a laminate of the ion exchange membrane A and anelectrode for electrolysis) was sandwiched between the gaskets. Here,both the ion exchange membrane A and the electrode for electrolysis weresandwiched directly between the gaskets. Then, the anode cell, thegasket, the laminate, the gasket, and the cathode were brought intoclose contact together to obtain an electrolytic cell, and anelectrolyzer including the cell was provided.

The anode was produced by applying a mixed solution of rutheniumchloride, iridium chloride, and titanium tetrachloride onto a titaniumsubstrate subjected to blasting and acid etching treatment as thepretreatment, followed by drying and baking. The anode was fixed in theanode chamber by welding. As the cathode, one described in each ofExamples and Comparative Examples was used. As the collector of thecathode chamber, a nickel expanded metal was used. The collector had asize of 95 mm in length×110 mm in width. As a metal elastic body, amattress formed by knitting nickel fine wire was used. The mattress asthe metal elastic body was placed on the collector. Nickel mesh formedby plain-weaving, nickel wire having a diameter of 150 μm in a sievemesh size of 40 was placed thereover, and a string made of Teflon(R) wasused to fix the four corners of the Ni mesh to the collector. This Nimesh was used as a feed conductor. This electrolytic cell has a zero-gapstructure by use of the repulsive force of the mattress as the metalelastic body. As the gaskets, ethylene propylene diene (EPDM) rubbergaskets were used. As the membrane, the ion exchange membrane A (160 mmsquare) produced in [Method (i)] was used.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted so as to allow the temperature in each electrolytic cell toreach 90° C. Common salt electrolysis was performed at a current densityof 6 kA/m² to measure the voltage, current efficiency, and common saltconcentration in caustic soda. The current efficiency here is theproportion of the amount of the produced caustic soda to the passedcurrent, and when impurity ions and hydroxide ions rather than sodiumions move through the on exchange membrane due to the passed current,the current efficiency decreases. The current efficiency was obtained bydividing the number of moles of caustic soda produced for a certain timeby the number of moles of the electrons of the current passing duringthat time. The number of moles of caustic soda was obtained byrecovering caustic soda produced by the electrolysis in a plasticcontainer and measuring its mass. As the common salt concentration incaustic soda, a value obtained by converting the caustic sodaconcentration on the basis of 50% was shown.

The specification of the electrode and the feed conductor used in eachof Examples and Comparative Examples is shown in Table 6.

(11) Measurement of Thickness of Catalytic Layer, Substrate forElectrode for Electrolysis, and Thickness of Electrode

For the thickness of the substrate for electrode for electrolysis, adigimatic thickness gauge (manufactured Mitutoyo Corporation, minimumscale 0.001 mm) was used to calculate an average value of 10 pointsobtained by measuring evenly in the plane. The value was used as thethickness of the substrate for electrode for electrolysis (gaugethickness). For the thickness of the electrode, a digimatic thicknessgauge was used to calculate an average value of 10 points obtained bymeasuring evenly in the plane, in the same manner as for the substratefor electrode. The value was used as the thickness of the electrode(gauge thickness). The thickness of the catalytic layer was determinedby subtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode.

(12) Elastic Deformation Test of Electrode

The ion exchange membrane A (membrane) and the electrode produced in[Method (i)] were each cut into a 110 mm square. The ion exchangemembrane was immersed in pure water for 12 hours or more and then usedfor the test. After the ion exchange membrane and the electrode werelaminated to produce a laminate under conditions of a temperature: 23±2°C. and a relative humidity: 30±5%, the laminate was wound around a PVCpipe having an outer diameter of ϕ32 mm and a length of 20 cm withoutany gap, as shown in FIG. 83. The laminate was fixed using apolyethylene cable tie such that the laminate wound did not come offfrom the PVC pipe or loosen. The laminate was retained in this state for6 hours. Thereafter, the cable tie was removed, and the laminate wasunwound from the PVC pipe. Only the electrode was placed on a surfaceplate, and the heights L₁ and L₂ of a portion lifted from the surfaceplate were measured to determine an average value. This value was usedas the index of the electrode deformation. That is, a smaller valuemeans that the laminate is unlikely to deform.

When an expanded metal is used, there are two winding direction: the SWdirection and the LW direction. In this test, the laminate was wound inthe SW direction.

Deformed electrodes (electrodes that did not return to their originalflat state) were evaluated for softness after plastic deformation inaccordance with a method as shown in FIG. 84. That is, a deformedelectrode was placed on a membrane sufficiently immersed in pure water.One end of the electrode was fixed, and the other lifted end was pressedonto the membrane to release a force, and an evaluation was performedwhether the deformed electrode conformed to the membrane.

(13) Membrane Damage Evaluation

As the membrane, an ion exchange membrane B below was used.

As reinforcement core material those obtained by twisting 100 deniertape yarns of polytetrafluoroethylene (PTFE) 900 times/m into a threadform were used (hereinafter referred to as PTFE yarns). As warpsacrifice yarns, yarns obtained by twisting eight 35 denier filaments ofpolyethylene terephthalate (PET) 200 times/m were used. (hereinafterreferred to as PET yarns). As weft sacrifice yarns, yarns obtained bytwisting eight 35 denier filaments of poly-ethylene terephthalate (PET)200 times/m were used. First, the PTFE yarns and the sacrifice yarnswere plain-woven with 24 PTFE yarns/inch so that two sacrifice yarnswere arranged between adjacent PTFE yarns, to obtain a woven fabrichaving a thickness of 100 μm.

Next, a polymer (A1) of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.92mg equivalent/g and a polymer (B1) of a dry resin that was a copolymerof CF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g were provided. Using these polymers(A1) and (B1), a two-layer film X in which the thickness of a polymer(A1) layer was 25 μm and the thickness of a polymer (31) layer was 89 μmwas obtained by a coextrusion T die method. As the ion exchange capacityof each polymer, shown was the ion exchange capacity in the case ofhydrolyzing the ion exchange group precursors of each polymer forconversion into ion exchange groups.

Separately, a polymer (B2) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.10 mg equivalent/g was provided. This polymer wassingle-layer extruded to obtain a film Y having a thickness of 20 μm.

Subsequently, release paper, the film Y, a reinforcing material, and thefilm X were laminated in this order on a hot plate having a heat sourceand a vacuum source inside and having micropores on its surface, heatedand depressurized under the conditions of a hot plate temperature of225° C. and a degree of reduced pressure of 0.022 MPa for two minutes,and then the release paper was removed to obtain a composite membrane.The resulting composite membrane was immersed in an aqueous solutioncomprising dimethyl sulfoxide (DMSO) and potassium hydroxide (KOH) foran hour for saponification. Thereafter, the membrane was immersed in0.5N NaOH for an hour to replace the ions attached to the ion exchangegroups by Na, and then washed with water. Further, the membrane wasdried at 60° C.

Additionally, a polymer (B3) of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.05 mg equivalent/g were hydrolyzed and then was turnedinto an acid type with hydrochloric acid. Zirconium oxide particleshaving an average particle size of primary particles of 0.02 μm wereadded to a 50/50 (mass ratio) mixed solution of water and ethanol inwhich the polymer (B3′) of this acid type was dissolved in a proportionof 5% by mass such that the mass ratio of the polymer (B3′) to thezirconium oxide particles was 20/80. Thereafter, the polymer (B3′) wasdispersed in a suspension of the zirconium oxide particles with a ballmill to obtain a suspension.

This suspension was applied by a spray method onto both the surfaces ofthe ion exchange membrane and dried to obtain an ion exchange membrane Bhaving a coating layer containing the polymer (B3′) and the zirconiumoxide particles. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.35 mg/cm².

The anode used was the same as in (9) Electrolytic evaluation.

The cathode used was one described in each of Examples and ComparativeExamples. The collector, mattress, and feed conductor of the cathodechamber used were the same as in (9) Electrolytic evaluation. That is, azero-gap structure had been provided by use of Ni mesh as the feedconductor and the repulsive force of the mattress as the metal elasticbody. The gaskets used were the same as in (9) Electrolytic evaluation.As the membrane, the ion exchange membrane B produced by the methodmentioned above was used. That is, an electrolyzer equivalent to that in(9) was provided except that the laminate of the ion exchange membrane Band the electrode for electrolysis was sandwiched between a pair ofgaskets.

The above electrolytic cell was used to perform electrolysis of commonsalt. The brine concentration (sodium chloride concentration) in theanode chamber was adjusted to 205 g/L. The sodium hydroxideconcentration in the cathode chamber was adjusted to 32% by mass. Thetemperature each in the anode chamber and the cathode chamber wasadjusted such that the temperature in each electrolytic cell reached 70°C. Common salt electrolysis was performed at a current density of 8kA/m². The electrolysis was stopped 12 hours after the start of theelectrolysis, and the ion exchange membrane B was removed and observedfor its damage condition.

“◯” means no damage. “×” means that damage was present on thesubstantially entire surface of the ion exchange membrane.

(14) Ventilation Resistance of Electrode

The ventilation resistance of the electrode was measured using an airpermeability tester KES-F8 (trade name, KATO TECH CO., LTD.). The unitfor the ventilation resistance value is kPa·s/m. The measurement wasrepeated 5 times, and the average value was listed in Table 7. Themeasurement was conducted under the following two conditions. Thetemperature of the measuring chamber was 24° C. and the relativehumidity was 32%.

Measurement Condition 1 (Ventilation Resistance 1)

Piston speed: 0.2 cm/s

Ventilation volume: 0.4 cc/cm²/s

Measurement range: SENSE L (low)

Sample size: 50 mm×50 mm

Measurement Condition 2 (Ventilation Resistance 2)

Piston speed: 2 cm/s

Ventilation volume: 4 cc/cm²/s

Measurement range: SENSE M (medium) or H (high)

Sample size: 50 mm×50 mm

Example 4-1

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 16 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.71 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by poaching. The opening ratio was 49%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced in Example 4-1 was 24μm. The thickness of the catalytic layer, which was determined bysubtracting the thickness of the substrate for electrode forelectrolysis from the thickness of the electrode, was 8 μm. The coatingwas formed also on the surface not roughened. The thickness was thetotal thickness of ruthenium oxide and cerium oxide.

The measurement results of the adhesive force of the electrode producedby the above method are shown in Table 7. A sufficient adhesive forcewas observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The roughenedsurface of the electrode was oppositely disposed on a substantial centerposition of the carboxylic acid layer side of the ion exchange membraneA (size: 160 mm×160 mm), produced in [Method (i)] and equilibrated witha 0.1 N NaOH aqueous solution, and allowed to adhere thereto via thesurface tension of the aqueous solution.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the electrode, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The above membrane-integrated electrode was sandwiched between the anodecell and the cathode cell such that the surface onto which the electrodewas attached was allowed to face the cathode chamber side. In thesectional structure, the collector, the mattress, the nickel mesh feedconductor, the electrode, the membrane, and the anode are arranged inthe order mentioned from the cathode chamber side to form a zero-gapstructure.

The resulting electrode was subjected to electrolytic evaluation. Theresults are shown in Table 7.

The electrode exhibited a low voltage, nigh current efficiency, and alow common salt concentration in caustic soda. The handling property wasalso good: “1”. The membrane damage was also evaluated as good: “0”.

When the amount of coating after the electrolysis was measured byfluorescent X-ray analysis (XRF), substantially 100% of the coatingremained on the roughened surface, and the coating on the surface notroughened was reduced. This indicates that the surface opposed to themembrane (roughened surface) contributes to the electrolysis and theother surface not opposed to the membrane can achieve satisfactoryelectrolytic performance when the amount of coating is small or nocoating is present.

Example 4-2

In Example 4-2, an electrolytic nickel foil having a gauge thickness of22 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 0.96 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 4-1, and theresults are shown in Table 7.

The thickness of the electrode was 29 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0033 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 4-3

In Example 4-3, an electrolytic nickel foil having a gauge thickness of30 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to roughening treatment bymeans of electrolytic nickel plating. The arithmetic average roughnessRa of the roughened surface was 1.38 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 44%. Except for the above described,evaluation was performed in the same manner as in Example 4-1, and theresults are shown in Table 7.

The thickness of the electrode was 38 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRF,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 4-4

In Example 4-4, an electrolytic nickel foil having a gauge thickness of16 μm was used as the substrate for electrode for cathode electrolysis.One surface of this nickel foil was subjected to a roughening treatmentby means of electrolytic nickel plating. The arithmetic averageroughness Ra of the roughened surface was 0.71 μm. The measurement ofthe surface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 75%. Except for the above described,evaluation was performed in the same manner as in Example 4-1, and theresults are shown in Table 7.

The thickness of the electrode was 24 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

When the amount of coating after the electrolysis was measured by XRT,substantially 100% of the coating remained on the roughened surface, andthe coating on the surface not roughened was reduced. This indicatesthat the surface opposed to the membrane (roughened surface) contributesto the electrolysis and the other surface not opposed to the membranecan achieve satisfactory electrolytic performance when the amount ofcoating is small or no coating is present.

Example 4-5

In Example 4-5, an electrolytic nickel foil having a gauge thickness of20 μm was provided as the substrate for electrode for cathodeelectrolysis. Both the surface of this nickel foil was subjected to aroughening treatment by means of electrolytic nickel plating. Thearithmetic average roughness Ra of the roughened surface was 0.96 μm.Both the surfaces had the same roughness. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. The opening ratio was 49%. Except for the above described,evaluation was performed in the same manner as in Example 4-1, and theresults are shown in Table 7.

The thickness of the electrode was 30 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm. The coating was formed also on the surface notroughened.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0023 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Additionally, when the amount of coating after the electrolysis wasmeasured by XRF, substantially 100% of the coating remained on both thesurface. In consideration of comparison with Examples 4-1 to 4-4, thisindicates that the other surface not opposed to the membrane can achievesatisfactory electrolytic performance when the amount of coating issmall or no coating is present.

Example 4-6

In Example 4-6, evaluation was performed in the same manner as inExample 4-1 except that coating of the substrate for electrode forcathode electrolysis was performed by ion plating, and the results areshown in Table 7. In the ion plating, film forming was performed using aheating temperature of 200° C. and Ru metal target under an argon/oxygenatmosphere at a film forming pressure of 7×10⁻² Pa. The coatrig formedwas ruthenium oxide.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-7

In Example 4-7, the substrate for electrode for cathode electrolysis wasproduced by an electroforming method. The photomask had a shape formedby vertically and horizontally arranging 0.485 mm×0.485 mm squares at aninterval of 0.15 mm. Exposure, development, and electroplating weresequentially performed to obtain a nickel porous foil having a gaugethickness of 20 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.71 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 37 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 17 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-8

In Example 4-8, the substrate for electrode for cathode electrolysis wasproduced by an electroforming method. The substrate had a gaugethickness of 50 μm and an opening ratio of 56%. The arithmetic averageroughness Ra of the surface was 0.73 μm. The measurement of the surfaceroughness was performed under the same conditions as for the surfaceroughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 60 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0032 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-9

In Example 4-9, a nickel nonwoven fabric having a gauge thickness of 150μm and a void ratio of 76% (manufactured by NIKKO TECHNO, Ltd.) was usedas the substrate for electrode for cathode electrolysis. The nonwovenfabric had a nickel fiber diameter of about 40 μm and a basis weight of300 g/m². Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 165 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 29 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less lender the measurementcondition 1 and 0.0612 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 4-10

In Example 4-10, a nickel nonwoven fabric having a gauge thickness of200 μm and a void ratio of 72% (manufactured by NIKKO TECHNO, Ltd.) wasused as the substrate for electrode for cathode electrolysis. Thenonwoven fabric had a nickel fiber diameter of about 40 μm and a basisweight of 500 g/m². Except for the above described, evaluation wasperformed in the same manner as in Example 4-1, and the results areshown in Table 7.

The thickness of the electrode was 215 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 15 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 40 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0164 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 4-11

In Example 4-11, foamed nickel having a gauge thickness of 200 μm and avoid ratio of 72% (manufactured by Mitsubishi Materials Corporation) wasused as the substrate for electrode for cathode electrolysis. Except forthe above described, evaluation was performed in the same manner as inExample 4-1, and the results are shown in Table 7.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 17 mm, and the electrode did not return to theoriginal flat state. Then, when softness after plastic deformation wasevaluated, the electrode conformed to the membrane due to the surfacetension. Thus, it was observed that the electrode was able to be broughtinto contact with the membrane by a small force even if the electrodewas plastically deformed and this electrode had a satisfactory handlingproperty.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0402 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was evaluated asgood: “0”.

Example 4-12

In Example 4-12, a 200-mesh nickel mesh having a line diameter of 50 μm,a gauge thickness of 100 μm, and an opening ratio of 37% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didnot change the opening ratio. It is difficult to measure the roughnessof the surface of the metal net. Thus, in Example 4-12, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra of a wire piece of the ire mesh was 0.64μm. The measurement of the surface roughness was performed under thesame conditions as for the surface roughness measurement of the nickelplate subjected to the blast treatment. Except for the above described,evaluation was performed in the same manner as in Example 4-1, and theresults are shown in Table 7.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L1 and P2. was 0.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0154 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also as good as “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-13

In Example 4-13, a 150-mesh nickel mesh having a line diameter of 65 μm,a gauge thickness of 130 μm, and an opening ratio of 38% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The blast treatment didhot change the opening ratio. It is difficult to measure the roughnessof the surface of the metal net. Thus, in Example 4-13, a nickel platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the nickelplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.66 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 4-1, and the results areshown in Table 7.

The thickness of the electrode was 133 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 3 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 6.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0124 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Theelectrode had a handling property of “2” and was determined to behandleable as a large laminate. The membrane damage was also evaluatedas good: “0”.

Example 4-14

In Example 4-14, a substrate identical to that of Example 4-3 (gaugethickness of 30 μm and opening ratio of 44%) was used as the substratefor electrode for cathode electrolysis. Electrolytic evaluation wasperformed with a structure identical to that of Example 4-1 except thatno nickel mesh feed conductor was included. That is, in the sectionalstructure of the cell, the collector, the mattress, themembrane-integrated electrode, and the anode are arranged in the ordermentioned from the cathode chamber side to form a zero-gap structure,and the mattress serves as the feed conductor. Except for the abovedescribed, evaluation was performed in the same manner as in Example4-1, and the results are shown in Table 7.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-15

In Example 4-15, a substrate identical to that of Example 4-3 (gaugethickness of 30 μm and opening ratio of 44%) was used as the substratefor electrode for cathode electrolysis. The cathode used in ReferenceExample 1, which was degraded and had an enhanced electrolytic voltage,was placed instead of the nickel mesh feed conductor. Except for theabove described, electrolytic evaluation was performed with a structureidentical to that of Example 4-1. That is, in the sectional structure ofthe cell, the collector, the mattress, the cathode that was degraded andhad an enhanced electro tic voltage (serves as the feed conductor), thecathode, the membrane, and the anode are arranged in the order mentionedfrom the cathode chamber side to form a zero-gap structure, and thecathode that is degraded and has an enhanced electrolytic voltage servesas the feed conductor. Except for the above described, evaluation wasperformed in the same manner as in Example 4-1, and the results areshown in Table 7.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L1 and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-16

A titanium foil having a gauge thickness of 20 μm was provided as thesubstrate for electrode for anode electrolysis. Both the surfaces of thetitanium foil were subjected to a roughening treatment. A porous foilwas formed by perforating this titanium foil with circular holes bypunching. The hole diameter was 1 mm, and the opening ratio was 14%. Thearithmetic average roughness Ra of the surface was 0.37 μm. Themeasurement of the surface roughness was performed under the sameconditions as for the surface roughness measurement of the nickel platesubjected to the blast treatment.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among, theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).After the above coating liquid was applied onto the titanium porousfoil, drying at 60° C. for 10 minutes and baking at 475° C. for 10minutes were performed. A series of these coating, drying, preliminarybaking, and baking operations was repeatedly performed, and then bakingat 520° C. was performed for an hour.

The electrode produced by the above method was cut into a size of 95 mmin length and 110 mm in width for electrolytic evaluation. The cutelectrode was allowed to adhere via the surface tension of the aqueoussolution to a substantial center position of the sulfonic acid layerside of the ion exchange membrane A (size: 160 mm×160 mm) produced in[Method (i)] and equilibrated with a 0.1 N NaOH aqueous solution.

The cathode was prepared in the following procedure. First, a 40-meshnickel wire mesh having a line diameter of 150 μm was provided as thesubstrate. After blasted with alumina as pretreatment, the wire mesh wasimmersed in 6 N hydrochloric acid for 5 minutes, sufficiently washedwith pure water, and dried.

Next, a ruthenium chloride solution having a ruthenium concentration of100 g/L (Tanaka Kikinzoku Kogyo K.K.) and cerium chloride (KISHIDACHEMICAL Co., Ltd.) were mixed such that the molar ratio between theruthenium element and the cerium element was 1:0.25. This mixed solutionwas sufficiently stirred and used as a cathode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 300°C. for 3 minutes, and baking at 550° C. for 10 minutes were performed.Thereafter, baking at 550° C. for an hour was performed. A series ofthese coating, drying, preliminary baking, and baking operations wasrepeated.

As the collector of the cathode chamber, a nickel expanded metal wasused. The collector had a size of 95 mm in length×110 mm in width. As ametal elastic body, a mattress formed by knitting nickel fine wire wasused. The mattress as the metal elastic body was placed on thecollector. The cathode produced by the above method was placedthereover, and a string made of Teflon(R) was used to fix the fourcorners of the mesh to the collector.

Even when the four corners of the membrane portion of themembrane-integrated electrode, which was formed by integrating themembrane with the anodes, were pinched and hung such that themembrane-integrated electrode was in parallel with the ground byallowing the electrode to face the ground side, the electrode did notcome off or was not displaced. Also when both the ends of one side werepinched and hung such that the membrane-integrated electrode wasvertical to the ground, the electrode did not come off or was notdisplaced.

The anode used in Reference Example 3, which was degraded and had anenhanced electrolytic voltage, was fixed to the anode cell by welding,and the above membrane-integrated electrode was sandwiched between theanode cell and the cathode cell such that the surface onto which theelectrode was attached was allowed to face the anode chamber side. Thatis, in the sectional structure of the cell, the collector, the mattress,the cathode, the membrane, the titanium porous foil anode, and the anodethat was degraded and had an enhanced electrolytic voltage were arrangedin the order mentioned from the cathode chamber side to form. a zero-gapstructure. The anode that was degraded and had an enhanced electrolyticvoltage served as the feed conductor. The titanium porous foil anode andthe anode that was degraded and had an enhanced electrolytic voltagewere only in physical contact with each other and were not fixed witheach other by welding.

Evacuation on this structure was performed in the same manner as inExample 4-1, and the results are shown in Table 7.

The thickness of the electrode was 26 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 6 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 4 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0060 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-17

In Example 4-17, a titanium foil having a gauge thickness of 20 μm andan opening ratio of 30% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.37 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example4-16, and the results are shown in Table 7.

The thickness of the electrode was 30 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 5 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-18

In Example 4-18, a titanium foil having a gauge thickness of 20 μm andan opening ratio of 42% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.38 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example4-16, and the results are shown in Table 7.

The thickness of the electrode was 32 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 12 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2.5 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0022 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-19

In Example 4-19, a titanium foil having a gauge thickness of 50 μm, andan opening ratio of 47% was used as the substrate for electrode foranode electrolysis. The arithmetic average roughness Ra of the surfacewas 0.40 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example4-16, and the results are shown in Table 7.

The thickness of the electrode was 69 μm. The thickness of the catalyticlayer, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 19 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 8 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0024 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-20

In Example 4-20, a titanium nonwoven fabric having a gauge thickness of100 μm, a titanium fiber diameter of about 20 μm, a basis weight of 100g/m², and an opening ratio of 78% was used as the substrate forelectrode for anode electrolysis. Except for the above described,evaluation was performed in the same manner as in Example 4-16, and theresults are shown in Table 7.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 2 mm. It was found that the electrode had a broadelastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0228 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-21

In Example 4-21, a 150-mesh titanium wire mesh having a gauge thicknessof 120 μm and a titanium fiber diameter of about 60 μm was used as thesubstrate for electrode for anode electrolysis. The opening ratio was42%. A blast treatment was performed with alumina of grain-size number320. It is difficult to measure the roughness of the surface of themetal net. Thus, in Example 4-21, a titanium plate having a thickness of1 mm was simultaneously subjected to the blast treatment during theblasting, and the surface roughness of the titanium plate was taken asthe surface roughness of the wire mesh. The arithmetic average roughnessRa was 0.60 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment Except for the abovedescribed, evaluation was performed in the same manner as in Example4-16, and the results are shown in Table 7.

The thickness of the electrode was 140 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 20 μm.

A sufficient adhesive force was observed.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 10 mm. It was found that the electrode had abroad elastic deformation region.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0132 (kPa·s/m) under the measurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0”.

Example 4-22

In Example 4-22, an anode that was degraded and had an enhancedelectrolytic voltage was used in the same manner as in Example 4-16 asthe anode feed conductor, and a titanium nonwoven fabric identical tothat of Example 4-20 was used as the anode. A cathode that was degradedand had an enhanced electrolytic voltage was used in the same manner asin Example 4-15 as the cathode feed conductor, and a nickel foilelectrode identical to that of Example 4-3 was used as the cathode. Inthe sectional structure of the cell, the collector, the mattress, thecathode that was degraded and had an enhanced voltage, the nickel porousfoil cathode, the membrane, the titanium nonwoven, fabric anode, and theanode that was degraded and had an enhanced electrolytic voltage arearranged in the order mentioned from the cathode chamber side to form azero-gap structure, and the cathode and anode degraded and having anenhanced electrolytic voltage serve as the feed conductor. Except forthe above described, evaluation was performed in the same manner as inExample 4-1, and the results are shown in Table 7.

The thickness of the electrode (anode) was 114 μm, and the thickness thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode (anode), was 14 μm. The thickness of the electrode (cathode)was 38 μm, and the thickness of the catalytic layer, which wasdetermined by subtracting the thickness of the substrate for electrodefor electrolysis from the thickness of the electro P (cathode), was 8μm.

A sufficient adhesive force was observed both in the anode and thecathode.

When a deformation test of the electrode (anode) was performed, theaverage value of L₁ and L₂ was 2 mm. When a deformation test of theelectrode (cathode) was performed, the average value of L₁ and L₂ was 0mm.

When the ventilation resistance of the electrode (anode) was measured,the ventilation resistance was 0.07 (kPa·s/m) or less under themeasurement condition and 0.0228 (kPa·s/m) under the measurementcondition 2. When the ventilation resistance of the electrode (cathode)was measured, the ventilation resistance was 0.07 (kPa·s/m) or lessunder the measurement condition 1 and 0.0027 (kPa·s/m) under themeasurement condition 2.

Additionally, the electrode exhibited a low voltage, high currentefficiency, and a low common salt concentration in caustic soda. Thehandling property was also good: “1”. The membrane damage was alsoevaluated as good: “0” both in the anode and the cathode. In Example4-22, the cathode and the anodes were combined by attaching the cathodeto one surface of the membrane and the anode to the other surface andsubjected to the membrane damage evaluation.

Example 4-23

In Example 4-23, a microporous membrane “Zirfon Perl UTP 500”manufactured by Agfa was used.

The Zirfon membrane was immersed in pure water for 12 hours or more andused for the test. Except for the above described, the above evaluationwas performed in the same manner as in Example 4-3, and the results areshown in Table 7.

When a deformation test the electrode was performed, the average valueof L₁ and L₂ was 0 mm. It was found that the electrode had a broadelastic deformation region.

Similarly to the case where an ion exchange membrane was used as themembrane, a sufficient adhesive force was observed. The microporousmembrane was brought into a close contact with the electrode via thesurface tension, and the handling property was good: “1”.

Reference Example 1

In Reference Example 1, used was a cathode used as the cathode in alarge electrolyzer for eight years, degraded, and having an enhancedelectrolytic voltage. The above cathode was placed instead of the nickelmesh feed conductor on the mattress of the cathode chamber, and the ionexchange membrane A produced in [Method (i)] was sandwichedtherebetween. Then, electrolytic evaluation was performed. In ReferenceExample 1, no membrane-integrated electrode was used. In the sectionalstructure of the cell, the collector, the mattress, the cathode that wasdegraded and had an enhanced electrolytic voltage, the ion exchangemembrane A, and the anodes were arranged in the order mentioned from thecathode chamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.04 V, the current efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was20 ppm. Consequently, due to degradation of the cathode, the voltage washigh.

Reference Example 2

In Reference Example 2, a nickel mesh feed conductor was used as thecathode. That is, electrolysis was performed on nickel mesh having nocatalyst coating thereon.

The nickel mesh cathode was placed on the mattress of the cathodechamber, and the ion exchange membrane A produced in [Method (i)] wassandwiched therebetween. Then, electrolytic evaluation was performed. Inthe sectional structure of the electric cell of Reference Example 2, thecollector, the mattress, the nickel mesh, the ion exchange membrane A,and the anodes were arranged in the order mentioned from the cathodechamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.38 V, the current efficiency was 97.7%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was24 ppm. Consequently, the voltage was high because the cathode catalysthad no coating.

Reference Example 3

In Reference Example 3, used was an anode used as the anode in a largeelectrolyzer for about eight years, degraded, and having an enhancedelectrolytic voltage.

In the sectional structure of the electrolytic cell of Reference Example3, the collector, the mattress, the cathode, the ion exchange membrane Aproduced in [Method (i)], and the anode that was degraded and had anenhanced electrolytic voltage were arranged in the order mentioned fromthe cathode chamber side to form a zero-gap structure.

As a result of the electrolytic evaluation with this structure, thevoltage was 3.18 V, the correct efficiency was 97.0%, the common saltconcentration in caustic soda (value converted on the basis of 50%) was22 ppm. Consequently, due to degradation of the anode, the voltage washigh.

Example 4-24

In Example 4-24, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 33% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of drain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-24, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.68 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 14 μm.

The mass per unit area was 67.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.05 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter was64%, and the result of evaluation of winding around column of 145 mm indiameter (3) was 22%. The portions at which the electrode came off fromthe membrane increased. This is because there were problems in that theelectrode was likely to come off when the membrane-integrated electrodewas handled and in that the electrode came off and fell from themembrane during handled. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Example 4-25

In Example 4-25, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 16% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-25, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.64 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 107 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm.

The mass per unit area was 78.1 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.04 (N/mg·cm2). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was 37%, and the result of evaluaton of winding around column of 145 mmin diameter (3) was 25%. The portions at which the electrode came offfrom the membrane increased. This is because there were problems in thatthe electrode was likely to come off when the membrane-integratedelectrode was handled and in that the electrode came off and fell fromthe membrane during handled. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 18.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition and 0.0176 (kPa·s/m) under the measurement condition 2.

Example 4-26

In Example 4-26, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 40% was used as thesubstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-26, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.70 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Coating of the substrate for electrode for electrolysis wasperformed by ion plating in the same manner as in Example 4-6. Exceptfor the above described, evaluation was performed in the same manner asin Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 110 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 10 μm.

The force applied per unit mass·unit area (1) was such a small value as0.07 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter (2) was 80%, and the result of evaluation ofwinding around column of 145 mm in diameter (3) was 32%. The portions atwhich the electrode came off from the membrane increased. This isbecause there were problems in that the electrode was likely to come offwhen the membrane-integrated electrode was handled and in that theelectrode came off and fell from the membrane during handled. Thehandling property was “3”, which was also problematic. The membranedamage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0030 (kPa·s/m) under the measurement condition 2.

Example 4-27

In Example 4-27, a fully-rolled nickel expanded metal having a gaugethickness of 100 μm and an opening ratio of 58% was used as theslibstrate for electrode for cathode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-27, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.64 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-1, and the results are shown in Table 7.

The thickness of the electrode was 109 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 9 μm.

The force applied per unit mass·unit area (1) was such a small value as0.06 (N/mg·cm²). Thus, the result of evaluation of winding around columnof 280 mm in diameter was 69%, and the result of evaluation of windingaround column of 145 mm in diameter (3) was 39%. The portions at whichthe electrode came off from the membrane increased. This is becausethere were problems in that the electrode was likely to come off whenthe membrane-integrated electrode was handled and in that the electrodecame off and fell from the membrane during handled. The handlingproperty was “3”, which was also problematic. The membrane damage wasevaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 11.5 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0028 (kPa·s/m) under the measurement condition 2.

Example 4-28

In Example 4-28, a nickel wire mesh having a gauge thickness of 300 μmand an opening ratio of 56% was used as the substrate for electrode forcathode electrolysis. It is difficult to measure the surface roughnessof the wire mesh. Thus, in Example 4-28, a nickel plate having athickness of 1 mm was simultaneously subjected to the blast treatmentduring the blasting, and the surface roughness of the nickel plate wastaken as the surface roughness of the wire mesh. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. The arithmetic average roughnessRa was 0.64 μm. The measurement of the surface roughness was performedunder the same conditions as for the surface roughness measurement ofthe nickel plate subjected to the blast treatment. Except for the abovedescribed, evaluation was performed in the same manner as in Example4-1, and the results are shown in Table 7.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 49.2 (mg/cm²). Thus, the result of evaluationof winding around column of 280 mm in diameter (2) was 88%, and theresult of evaluation of winding around column of 145 mm in diameter (3)was 42%. The portions at which the electrode came off from the membraneincreased. This is because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehandling property, which was evaluated as “3”. When the large sizeelectrode was actually operated, it was possible to evaluate thehandling property as “3”. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

Example 4-29

In Example 4-29, a nickel wire mesh having a gauge thickness of 200 μmand an opening ratio of 37% was used as the substrate for electrode forcathode electrolysis. A blast treatment was performed with alumina ofgrain-size number 320. The opening ratio was not changed after the blasttreatment. It is difficult to measure the surface roughness of the wiremesh. Thus, in Example 4-29, a nickel plate having a thickness of 1 mmwas simultaneously subjected to the blast treatment during the blasting,and the surface roughness of the nickel plate was taken as the surfaceroughness of the wire mesh. The arithmetic average roughness Ra was 0.65μm. The measurement of the surface roughness was performed under thesame conditions as for the surface roughness measurement of the nickelplate subjected to the blast treatment. Except for the above described,evaluation of electrode electrolysis, measurement results of theadhesive force, and adhesiveness were performed in the same manner as inExample 4-1. The results are shown in Table 7.

The thickness of the electrode was 210 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness or theelectrode, was 10 μm.

The mass per unit area was 56.4 (mg/cm²). Thus, the result of evaluationmethod of winding around column of 145 mm in diameter (3) was 63%, andthe adhesiveness between the electrode and the membrane was poor. Thisis because the electrode was likely to come off when themembrane-integrated electrode is handled and the electrode may come offand fall from the membrane during handled. There was a problem in thehandling property, which was evaluated as “3”. The membrane damage wasevaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 19 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0096 (kPa·s/m) under the measurement condition 2.

Example 4-30

In Example 4-30, a full-rolled titanium expanded metal having a gaugethickness of 500 μm and an opening ratio of 17% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-30, atitanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.60 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, evaluation was performed inthe same manner as in Example 4-16, and the results are shown in Table7.

The thickness of the electrode was 508 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 152.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of windng around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane during:handled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0072 (kPa·s/m) under the measurement condition 2.

Example 4-31

In Example 4-31, a full-rolled titanium expanded metal having a gaugethickness of 800 μm and an opening ratio of 8% was used as the substratefor electrode for anode electrolysis. A blast treatment was performedwith alumina of grain-size number 320. The opening ratio was not changedafter the blast treatment. It is difficult to measure the surfaceroughness of the expanded metal. Thus, in Example 4-31, a titanium platehaving a thickness of 1 mm was simultaneously subjected to the blasttreatment during the blasting, and the surface roughness of the titaniumplate was taken as the surface roughness of the wire mesh. Thearithmetic average roughness Ra was 0.61 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 4-16, and the results areshown in Table 7.

The thickness of the electrode was 808 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

The mass per unit area was 251.3 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0172 (kPa·s/m) under the measurement condition 2.

Example 4-32

In Example 4-32, a full-rolled titanium expanded metal having a gaugethickness of 1000 μm and an opening ratio of 46% was used as thesubstrate for electrode for anode electrolysis. A blast treatment wasperformed with alumina of grain-size number 320. The opening ratio wasnot changed after the blast treatment. It is difficult to measure thesurface roughness of the expanded metal. Thus, in Example 4-32, atitanium plate having a thickness of 1 mm was simultaneously subjectedto the blast treatment during the blasting, and the surface roughness ofthe titanium plate was taken as the surface roughness of the wire mesh.The arithmetic average roughness Ra was 0.59 μm. The measurement of thesurface roughness was performed under the same conditions as for thesurface roughness measurement of the nickel plate subjected to the blasttreatment. Except for the above described, the above evaluation wasperformed in the same manner as in Example 4-16, and the results areshown in Table 7.

The thickness of the electrode was 1011 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 11 μm.

The mass per unit area was 245.5 (mg/cm²). The force applied per unitmass·unit area (1) was such a small value as 0.01 (N/mg·cm²). Thus, theresult of evaluation of winding around column of 280 mm in diameter (2)was less than 5%, and the result of evaluation of winding around columnof 145 mm in diameter (3) was less than 5%. The portions at which theelectrode came off from the membrane increased. This is because theelectrode was likely to come off when the membrane-integrated electrodewas handled, the electrode came off and fell from the membrane duringhandled, and so on. The handling property was “4”, which was alsoproblematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the electrodedid not recover and remained rolled up in the PVC pipe form. Thus, itwas not possible to measure the values of L₁ and L₂.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0027 (kPa·s/m) under the measurement condition 2.

Example 4-33

In Example 4-33, a membrane electrode assembly was produced by thermallycompressing an electrode onto a membrane with reference to a prior artdocument (Examples of Japanese Patent Laid-Open No. 58-48686).

A nickel expanded metal having a gauge thickness of 100 μm and anopening ratio or 33% was used as the substrate for electrode for cathodeelectrolysis to Perform electrode coating in the same manner as inExample 4-1. Thereafter, one surface of the electrode was subjected toan inactivation treatment in the following procedure. Polyimide adhesivetape (Chukoh Chemical Industries, Ltd.) was attached to one surface ofthe electrode. A PTFE dispersion (Dupont-Mitsui Fluorochemicals Co.,Ltd., 31-JR (trade name)) was applied onto the other surface and driedin a muffle furnace at 120° C. for 10 minutes. The polymide tape waspeeled off, and a sintering treatment was performed in a muffle furnaceset at 380° C. for 10 minutes. This operation was repeated twice toinactivate the one surface of the electrode.

Produced was a membrane formed by two layers of a perfluorocarbonpolymer of which terminal functional group is “—COOCH₃” (C polymer) anda perfluorocarbon polymer of which terminal functional group is “—SO₂F”(S polymer). The thickness of the C polymer layer was 3 mils, and thethickness of the S polymer layer was 4 mils. This two-layer membrane wassubjected to a saponification treatment to thereby introduce ionexchange groups to the terminals of the polymer by hydrolysis. The Cpolymer terminals were hydrolyzed into carboxylic acid groups and the Spolymer terminals into sulfo groups. The ion exchange capacity as thesulfonic acid group was 1.0 meq/g, and the ion exchange capacity as thecarboxylic acid group was 0.9 meq/g.

The inactivated electrode surface was oppositely disposed to andthermally pressed onto the surface having carboxylic acid groups as theion exchange groups to integrate the ion exchange membrane and theelectrode. The one surface of the electrode was exposed even after thethermal compression, and the electrode passed through no portion of themembrane.

Thereafter, in order to suppress attachment of bubbles to be generatedduring electrolysis to the membrane, a mixture of zirconium oxide and aperfluorocarbon polymer into which sulfo groups had been introduced wasapplied onto both the surfaces. Thus, the membrane electrode assembly ofExample 4-33 was produced.

When the force applied per unit mass·unit area (1) was measured usingthis membrane electrode assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.50 (N/mg·cm²) was applied, aportion of the membrane was broken. The membrane electrode assembly ofExample 4-33 had a force applied per unit mass·unit area (1) of at least1.50 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed, the area in contact with the plastic pipe was less than 5%.Meanwhile, when evaluation of winding around column of 280 mm indiameter (2) was performed, the electrode and the membrane were 100%bonded to each other, but the membrane was not wound around the columnin the first place. The result of evaluation of winding around column of145 mm (3) was the same. The result meant that the integrated electrodeimpaired the handling property of the membrane to thereby make itdifficult to roll the membrane into a roil and fold the membrane. Thehandling property was “3”, which was problematic. The membrane damagewas evaluated as “0”. Additionally, when electrolytic evaluation wasperformed, the voltage was high, the current efficiency was low, thecommon salt concentration in caustic soda (value converted on the basisof 50%) was raised, and the electrolytic performance deteriorated.

The thickness of the electrode was 114 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 14 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 13 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0168 (kPa·s/m) under the measurement condition 2.

Example 4-34

In Example 4-34, a 40-mesh nickel mesh having a line diameter of 150 μm,a gauge thickness of 300 μm, and an opening ratio of 58% was used as thesubstrate for electrode for cathode electrolysis. Except for the abovedescribed, a membrane electrode assembly was produced in the same manneras in Example 4-33.

When the force applied per unit mess·unit area (1) was measured usingthis membrane electrode assembly, the electrode did not move upwardbecause the electrode and the membrane were tightly bonded to each othervia thermal compression. Then, the ion exchange membrane and nickelplate were fixed so as not to move, and the electrode was pulled upwardby a stronger force. When a force of 1.60 (N/mg·cm²) was applied, aportion of the membrane was broken. The membrane electrode assembly ofExample 4-34 had a force applied per unit mass·unit area (1) of at least1.60 (N/mg·cm²) and was strongly bonded.

When evaluation of winding around column of 280 mm in diameter (1) wasperformed using this membrane electrode assembly, the contact area withthe plastic pipe was less than 5%. Meanwhile, when evaluation of windingaround column of 280 mm in diameter (2) was performed, the electrode andthe membrane were 100% bonded to each other, but the membrane was notwound around the column in the first place. The result of evaluation ofwinding around column of 145 mm (3) was the same. The result meant thatthe integrated electrode impaired the handling property of the membraneto thereby make it difficult to roll the membrane into a roll and foldthe membrane. The handling property was “3”, which was problematic.Additionally, when electrolytic evaluation was performed, the voltagewas high, the current efficiency was low, the common salt concentrationin caustic soda was raised, and the electrolytic performancedeteriorated.

The thickness of the electrode was 308 μm. The thickness of thecatalytic layer, which was determined by subtracting the thickness ofthe substrate for electrode for electrolysis from the thickness of theelectrode, was 8 μm.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 23 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.07 (kPa·s/m) or less under the measurementcondition 1 and 0.0034 (kPa·s/m) under the measurement condition 2.

Example 4-35

A nickel line having a gauge thickness of 150 μm was provided as thesubstrate for electrode for cathode electrolysis. A roughening treatmentby this nickel line was performed. It is difficult to measure thesurface roughness of the nickel line. Thus, in Example 4-35, a nickelplate having a thickness of 1 mm was simultaneously subjected to theblast treatment during the blasting, and the surface roughness of thenickel plate was taken as the surface roughness of the nickel line. Ablast treatment was performed with alumina of grain-size number 320. Thearithmetic average roughness Ra was 0.64 μm.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure ruthenium nitrate solution having a rutheniumconcentration of 100 g/L (FURUYA METAL Co., Ltd.) and cerium nitrate(KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molar ratiobetween the ruthenium element and the cerium element t was 1:0.25. Thismixed solution was sufficiently stirred and used as a cathode coatingliquid.

A vat containing, the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088 (tradename), thickness 10 mm) around a chloride (PVC) cylinder was always incontact with the above coating liquid. A coating roil around which thesame EPDM had been wound was laced at the upper portion thereof, and aPVC roller was further placed thereabove. The coating liquid was appliedby allowing the substrate for electrode to pass between the secondcoating roll and the PVC roller at the uppermost portion (roll coatingmethod). Then, after drying at 50° C. for 10 minutes, preliminary bakingat 150° C. for 3 minutes, and baking at 350° C. for 10 minutes wereperformed. A series of these coating, drying, preliminary baking, andbaking operations was repeated until a predetermined amount of coatingwas achieved. The thickness of one nickel line produced in Example 4-35was 158 μm.

The nickel line produced h the above method was cut into a length of 110mm and a length of 95 mm. As shown in FIG. 85, the 110 mm nickel lineand the 95 mm nickel line were placed such that the nickel linesvertically overlapped each other at the center of each of the nickellines and bonded to each other at the intersection with. Aron Alpha toproduce an electrode. The electrode was evaluated, and the results areshown in Table 7.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.7%.

The mass per unit area of the electrode was 0.5 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 15 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance value was 0.0002(kPa·s/m).

Additionally, the structure shown in FIG. 86 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.16 V.

Example 4-36

In Example 4-36, the electrode produced in Example 4-35 was used. Asshown in FIG. 87, the 110 mm nickel line and the 95 mm nickel line wereplaced such that the nickel lines vertically overlapped each other atthe center of each of the nickel lines and bonded to each other at theintersection with Aron Alpha to produce an electrode. The electrode wasevaluated, and the results are shown in Table 7.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was99.4%.

The mass per unit area of the electrode was 0.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 16 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0004 (kPa·s/m).

Additionally, the structure shown in FIG. 88 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

Example 4-37

In Example 4-37, the electrode produced in Example 4-35 was used. Asshown in FIG. 89, the 110 mm nickel line and the 95 mm nickel line wereplaced such that the nickel lines vertically overlapped each other atthe center of each of the nickel lines and bonded to each other at theintersection with Aron Alpha to produce an electrode. The electrode wasevaluated, and the results are shown in Table 7.

The portion of the electrode at which the nickel lines overlapped hadthe largest thickness, and the thickness of the electrode was 306 μm.The thickness of the catalytic layer was 6 μm. The opening ratio was98.8%.

The mass per unit area of the electrode was 1.9 (mg/cm²). The forcesapplied per unit mass·unit area (1) and (2) were both equal to or lessthan the measurement lower limit of the tensile testing machine. Thus,the result of evaluation of winding around column of 280 mm in diameter(1) was less than 5%, and the portions at which the electrode came offfrom the membrane increased. The handling property was “4”, which wasalso problematic. The membrane damage was evaluated as “0”.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 14 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 0.001 (kPa·s/m) or less under the measurementcondition 2. When measured under the measurement condition 2 with SENSE(measurement range) set at H (high) of the ventilation resistancemeasurement apparatus, the ventilation resistance was 0.0005 (kPa·s/m).

Additionally, the structure shown in FIG. 90 was used to place theelectrode (cathode) on the Ni mesh feed conductor, and electrolyticevaluation of the electrode was performed by the method described in (9)Electrolytic evaluation. As a result, the voltage was as high as 3.18 V.

Comparative Example 4-1 (Preparation of Catalyst)

A metal salt aqueous solution was produced by adding 0.728 g of silvernitrate (Wako Pure Chemical Industries, Ltd.) and 1.86 g of ceriumnitrate hexahydrate (Wako Pure Chemical Industries, Ltd.) to 150 ml ofpure water. An alkali solution was produced by adding 240 g of purewater to 100 g of a 15% tetramethylammonium hydroxide aqueous solution(Wako Pure Chemical Industries, Ltd.). While the alkali solution wasstirred using a magnetic stirrer, the metal salt aqueous solution wasadded thereto dropwise at 5 ml/minute using a buret. A suspensioncontaining the resulting metal hydroxide particulates wassuction-filtered and then washed with water to remove the alkalicontent. Thereafter, the residue was transferred into 200 ml of2-propanol (KISHIDA CHEMICAL Co., Ltd.) and redispersed by an ultrasonicdispersing apparatus (US-600T, NISSEI Corporation) for 10 minutes toobtain a uniform suspension.

A suspension of carbon black was obtained by dispersing 0.36 g ofhydrophobic carbon black (DENKA BLACK(R) AB-7 (trade name), DenkaCompany Limited) and 0.84 g of hydrophilic carbon black (Ketjenblack(R)EC-600JD (trade name), Mitsubishi Chemical Corporation) in 100 ml of2-propanol and dispersing the mixture by the ultrasonic dispersingapparatus for 10 minutes. The metal hydroxide precursor suspension andthe carbon black suspension were mixed and dispersed by the ultrasonicdispersing apparatus for 10 minutes. This suspension was such and driedat room temperature for half a day to obtain carbon black containing themetal hydroxide precursor dispersed and fixed. Subsequently, an inertgas baking furnace (VMF165 type, YAMADA DENKI CO., LTD.) was used toperform baking in a nitrogen atmosphere at 400° C. for an hour to obtaincarbon black A containing an electrode catalyst dispersed and fixed.

(Production of Powder for Reaction Layer)

In 1.6 g of the carbon black A containing an electrode catalystdispersed and fixed, 0.84 ml of a surfactant Triton(R) X-100(trade name,ICN Biomedicals) diluted to 20% by weight with pure water and 15 ml ofpure water, and the mixture was dispersed by an ultrasonic dispersingapparatus for 10 minutes. To this dispersion, 0.664 g of apolytetrafluoroethylene (PTFE) dispersion (PTFE30J (trade name),Dupont-Mitsui Fluorochemicals Co., Ltd.) was added. After the mixturewas stirred for five minutes, suction filtration was performed.Additionally, the residue was dried in a dryer at 80° C. for an hour,and pulverization was performed by a mill to obtain a powder forreaction layer A.

(Production of Powder for Gas Diffusion Layer)

Dispersed were 20 g of hydrophobic carbon black (DENKA BLACK(R) AB-7(trade name)), 50 ml of a surfactant. Triton(R) X-100(trade name)diluted to 20% by weight with pure water, and 360 ml of pure water by anultrasonic dispersing apparatus for 10 minutes. To the resultingdispersion, 22.32 g of the PTFE dispersion was added. The mixture wasstirred for 5 minutes, and then, filtration was performed. Additionally,the residue was dried in a dryer at 80° C. for an hour, andpulverization was performed by a mill to obtain a powder for gasdiffusion layer A.

(Production of Gas Diffusion Electrode)

To 4 g of the powder for gas diffusion layer A, 8.7 ml of ethanol wasadded, and the mixture was kneaded into a paste form. This powder forgas diffusion layer in a paste form was formed into a sheet form by aroll former. Silver mesh (SW=1, LW=2, and thickness=0.3 mm) as thecollector was embedded into the sheet and finally formed into a sheetform having a thickness of 1.8 mm. To 1 g of the powder for reactionlayer A, 2.2 ml of ethanol was added, and the mixture was kneaded into apaste form. This powder for reaction layer in a paste form was formedinto a sheet form having a thickness of 0.2 mm by a roll former.Additionally, the two sheets, that is, the sheet obtained by using thepowder for gas diffusion layer A produced and the sheet obtained byusing the powder for reaction layer A were laminated and formed into asheet form having a thickness of 1.8 mm by a roll former. This laminatedsheet was dried at room temperature for a whole day and right to removeethanol. Further, in order to remove the remaining surfactant, the sheetwas subjected to a pyrolysis treatment in air at 300° C. for an hour.The sheet was wrapped in an aluminum foil, and subjected to hot pressingby a hot pressing machine (SA303 (trade name), TESTER SANGYO CO., LTD.)at 360° C. and 50 kgf/cm² for 1 minute to obtain a gas diffusionelectrode. The thickness of the gas diffusion electrode was 412 μm.

The resulting electrode was used to perform electrolytic evaluation. Inthe sectional structure of the electrolytic cell, the collector, themattress, the nickel mesh feed conductor, the electrode, the membrane,and the anode are arranged in the order mentioned from the cathodechamber side to form a zero-gap structure. The results are shown inTable 7.

When a deformation test of the electrode was performed, the averagevalue of L₁ and L₂ was 19 mm.

When the ventilation resistance of the electrode was measured, theventilation resistance was 25.88 (kPa·s/m) under the measurementcondition 1.

The handling property was “3”, which was problematic. Additionally, whenelectrolytic evaluation was performed, the current efficiency was low,the common salt concentration in caustic soda was raised and theelectrolytic performance markedly deteriorated. The membrane damage,which was evaluated as “3”, also had a problem.

These results have revealed that the gas diffusion electrode obtained inComparative Example 4-1 had markedly poor electrolytic performance.Additionally, damage was observed on the substantially entire surface ofthe ion exchange membrane. It was conceived that this is because NaOHthat had been generated in the electrode accumulated on the interfacebetween the electrode and the membrane to elevate the concentrationthereof, due to the markedly high ventilation resistance of the gasdiffusion electrode of Comparative Example 4-1.

TABLE 6 Substrate for Form of substrate Coating electrode for electrodemethod Feed conductor Example 4-1 Ni Punching Pyrolysis Ni mesh Example4-2 Ni Punching Pyrolysis Ni mesh Example 4-3 Ni Punching Pyrolysis Nimesh Example 4-4 Ni Punching Pyrolysis Ni mesh Example 4-5 Ni PunchingPyrolysis Ni mesh Example 4-6 Ni Punching Ion plating Ni mesh Example4-7 Ni Electroforming Pyrolysis Ni mesh Example 4-8 Ni ElectroformingPyrolysis Ni mesh Example 4-9 Ni Nonwoven fabric Pyrolysis Ni meshExample 4-10 Ni Nonwoven fabric Pyrolysis Ni mesh Example 4-11 Ni FoamedNi Pyrolysis Ni mesh Example 4-12 Ni Mesh Pyrolysis Ni mesh Example 4-13Ni Mesh Pyrolysis Ni mesh Example 4-14 Ni Punching (same PyrolysisMattress as in Example 4-3) Example 4-15 Ni Punching (same PyrolysisCathode having increase in voltage as in Example 4-3) Example 4-16 TiPunching Pyrolysis Anode having increase in voltage Example 4-17 TiPunching Pyrolysis Anode having increase in voltage Example 4-18 TiPunching Pyrolysis Anode having increase in voltage Example 4-19 TiPunching Pyrolysis Anode having increase in voltage Example 4-20 TiNonwoven fabric Pyrolysis Anode having increase in voltage Example 4-21Ti Mesh Pyrolysis Anode having increase in voltage Example 4-22 Ni/TiCombination of Pyrolysis Cathode and anode having increase in voltageExample 4-3 and Example 4-20 Example 4-23 Ni Punching Pyrolysis —Example 4-24 Ni Expanded Pyrolysis Ni mesh Example 4-25 Ni ExpandedPyrolysis Ni mesh Example 4-26 Ni Expanded Ion plating Ni mesh Example4-27 Ni Expanded Pyrolysis Ni mesh Example 4-28 Ni Mesh Pyrolysis Nimesh Example 4-29 Ni Mesh Pyrolysis Ni mesh Example 4-30 Ti ExpandedPyrolysis Anode having increase in voltage Example 4-31 Ti ExpandedPyrolysis Anode having increase in voltage Example 4-32 Ti ExpandedPyrolysis Anode having increase in voltage Example 4-33 Ni ExpandedPyrolysis Ni mesh Example 4-34 Ni Mesh Pyrolysis Ni mesh Example 4-35 NiMesh Pyrolysis Ni mesh Example 4-36 Ni Mesh Pyrolysis Ni mesh Example4-37 Ni Mesh Pyrolysis Ni mesh Comparative Carbon Powder Pyrolysis Nimesh Example 4-1

TABLE 7 Thickness of substrate for electrode for Thickness of ThicknessMass per Force applied per unit electrolysis electrode of catalyticOpening ratio unit area mass · unit area (1) (μm) (μm) layer (μm) (voidratio) % (mg/cm²) (N/mg · cm²-electrode) Example 4-1 16 24 8 49 5.8 0.90Example 4-2 22 29 7 44 9.9 0.61 Example 4-3 30 38 8 44 11.1 0.43 Example4-4 16 24 8 75 3.5 0.28 Example 4-5 20 30 10 49 6.4 0.59 Example 4-6 1626 10 49 6.2 0.81 Example 4-7 20 37 17 56 8.1 0.79 Example 4-8 50 60 1056 18.1 0.13 Example 4-9 150 165 15 76 31.9 0.22 Example 4-10 200 215 1572 46.3 0.12 Example 4-11 200 210 10 72 36.5 0.13 Example 4-12 100 11010 37 27.4 0.18 Example 4-13 130 133 3 38 36.3 0.15 Example 4-14 30 38 844 11.1 0.43 Example 4-15 30 38 8 44 11.1 0.43 Example 4-16 20 26 5 148.9 0.16 Example 4-17 20 30 10 30 8.1 0.26 Example 4-18 20 32 12 42 6.60.24 Example 4-19 50 69 19 47 12.9 0.12 Example 4-20 100 114 14 78 11.30.59 Example 4-21 120 140 20 42 14.9 0.47 Example 4-22 30/100 38/1148/14 44/78 11.1/11.3 0.43/0.59 Example 4-23 30 38 8 44 11.1 0.28 Example4-24 100 114 14 33 67.5 0.05 Example 4-25 100 107 7 16 78.1 0.04 Example4-26 100 110 10 40 37.8 0.07 Example 4-27 100 109 9 58 39.2 0.06 Example4-28 300 308 8 56 49.2 0.18 Example 4-29 200 210 10 37 56.4 0.09 Example4-30 500 508 8 17 152.5 0.01 Example 4-31 800 808 8 8 251.3 0.01 Example4-32 1000 1011 11 46 245.5 0.01 Example 4-33 100 114 14 33 67.5 1.50Example 4-34 300 308 8 58 49.2 1.80 Example 4-35 300 306 6 99 0.5 Equalto or less than the measurement lower limit Example 4-36 300 306 10 990.9 Equal to or less than the measurement lower limit Example 4-37 300306 15 99 1.9 Equal to or less than the measurement lower limitComparative Example 4-1 412 412 — — 101 0.005 Method for Method forMethod for evaluating evaluating evaluating winding winding windingaround around around column of column of column of 280 mm in 145 mm in280 mm in diameter (2) diameter (3) diameter (1) (membrane (membraneHanding Force applied per unit (membrane and and property mass · unitarea (2) and column) electrode) electrode) (sensory (N/mg ·cm²-electrode) (%) (%) (%) evaluation) Example 4-1 0.640 100 100 100 1Example 4-2 0.235 100 100 100 1 Example 4-3 0.194 100 100 100 1 Example4-4 0.113 100 100 100 1 Example 4-5 0.386 100 100 100 1 Example 4-60.650 100 100 100 1 Example 4-7 0.184 100 100 100 1 Example 4-8 0.088100 100 100 1 Example 4-9 0.217 100 100 100 2 Example 4-10 0.081 100 10079 2 Example 4-11 0.162 100 100 100 2 Example 4-12 0.126 100 100 100 1Example 4-13 0.098 100 100 88 2 Example 4-14 0.194 100 100 100 1 Example4-15 0.194 100 100 100 1 Example 4-16 0.105 100 100 100 1 Example 4-170.132 100 100 100 1 Example 4-18 0.147 100 100 100 1 Example 4-19 0.08100 100 100 1 Example 4-20 0.378 100 100 100 1 Example 4-21 0.308 100100 100 1 Example 4-22 0.194/0.378 100/100 100/100 100/100 1/1 Example4-23 0.194 100 100 100 1 Example 4-24 0.045 100 64 22 4 Example 4-250.027 100 37 25 4 Example 4-26 0.045 100 80 32 3 Example 4-27 0.034 10069 39 3 Example 4-28 0.138 100 88 42 3 Example 4-29 0.060 100 100 63 3Example 4-30 0.005 100 Less than 5 Less than 5 4 Example 4-31 0.006 100Less than 5 Less than 5 4 Example 4-32 0.005 100 Less than 5 Less than 54 Example 4-33 — Less than 5 — — 3 Example 4-34 — Less than 5 — — 3Example 4-35 Equal to or less than the Less than 5 — — 4 measurementlower limit Example 4-36 Equal to or less than the Less than 5 — — 4measurement lower limit Example 4-37 Equal to or less than the Less than5 — — 4 measurement lower limit Comparative Example 4-1 0.005 Less than5 — — 3 Elastic deformation test of electrode Electrolytic evaluation(winding around Common salt vinyl chloride Ventilation Ventilationconcentration pipe of 32 mm in resistance resistance Current in causticsoda outer diameter) (KPa · s/m) (KPa · s/m) Membrane Voltage efficiency(ppm, on the average value of (measurement (measurement damage (V) (%)basis of 50%) L₁ and L₂ (mm) condition 1) condition 2) evaluationExample 4-1 2.98 97.7 15 0 0.07 or less 0.0028 ∘ Example 4-2 2.95 97.218 0 0.07 or less 0.0033 ∘ Example 4-3 2.96 97.6 19 0 0.07 or less0.0027 ∘ Example 4-4 2.97 97.5 15 0 0.07 or less 0.0023 ∘ Example 4-52.95 97.1 18 0 0.07 or less 0.0023 ∘ Example 4-6 2.96 97.3 14 0 0.07 orless 0.0028 ∘ Example 4-7 2.96 97.3 15 0 0.07 or less 0.0032 ∘ Example4-8 2.96 97.7 16 0 0.07 or less 0.0032 ∘ Example 4-9 2.97 96.8 23 290.07 or less 0.0612 ∘ Example 4-10 2.96 96.7 26 40 0.07 or less 0.0154 ∘Example 4-11 3.05 97.4 22 17 0.07 or less 0.0402 ∘ Example 4-12 3.1197.2 23 0.5 0.07 or less 0.0154 ∘ Example 4-13 3.09 97.0 25 5.5 0.07 orless 0.0124 ∘ Example 4-14 2.97 97.3 18 0 0.07 or less 0.0027 ∘ Example4-15 2.96 97.2 21 0 0.07 or less 0.0027 ∘ Example 4-16 3.10 96.8 19 40.07 or less 0.0060 ∘ Example 4-17 3.07 96.8 26 5 0.07 or less 0.0030 ∘Example 4-18 3.08 97.7 21 2.5 0.07 or less 0.0022 ∘ Example 4-19 3.0997.0 21 8 0.07 or less 0.0024 ∘ Example 4-20 2.97 96.8 24 2 0.07 or less0.0228 ∘ Example 4-21 2.99 97.0 18 10 0.07 or less 0.0132 ∘ Example 4-223.00 97.2 17 0/2 0.07 or less 0.0027/0.0228 ∘ Example 4-23 — — — 0 0.07or less 0.0027 ∘ Example 4-24 2.98 97.7 19 13 0.07 or less 0.0168 ∘Example 4-25 2.99 97.8 17 18.5 0.07 or less 0.0176 ∘ Example 4-26 2.9697.5 18 11 0.07 or less 0.0030 ∘ Example 4-27 2.99 97.6 18 11.5 0.07 orless 0.0028 ∘ Example 4-28 2.95 97.5 24 23 0.07 or less 0.0034 ∘ Example4-29 2.98 97.3 23 19 0.07 or less 0.0096 ∘ Example 4-30 2.99 96.7 23Remained 0.07 or less 0.0072 ∘ Example 4-31 3.02 97.0 19 deformed in0.07 or less 0.0172 ∘ Example 4-32 3.00 97.2 20 vinyl chloride 0.07 orless 0.0027 ∘ form and did not return Example 4-33 3.67 93.8 226 13 0.07or less 0.0168 ∘ Example 4-34 3.71 94.5 155 23 0.07 or less 0.0034 ∘Example 4-35 3.16 97.5 21 15 0.07 or less 0.0002 ∘ Example 4-36 3.1897.4 19 16 0.07 or less 0.0004 ∘ Example 4-37 3.18 97.3 20 14 0.07 orless 0.0005 ∘ Comparative Example 4-1 3.65 48.0 680 19 25.88 — x

In Table 7, all the samples were able to stand by themselves by thesurface tension before measurement of “force applied per unit mass·unitarea (1)” and “force applied per unit mass·unit area (2)” (i.e., did notslip down).

<Verification of Fifth Embodiment>

As will be described below, Experiment Examples according to the fifthembodiment (in the section of <Verification of fifth embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the fifth embodiment (in the section of <Verificationof fifth embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 93 to 94 and 100 to102 as appropriate.

As the membrane, an ion exchange membrane A produced as described belowwas used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTFE) were used (hereinafter referred to asPTFE yarns). As the sacrifice yarns, yarns obtained by twisting, six 35denier filaments of polyethylene terephthalate (PET) 200 times/m wereused (hereinafter referred to as PET yarns). First, in each of the TDand the MD, the PTFE yarns and the sacrifice yarns were plain-woven with24 PTFE yarns/inch so that sacrifice yarns were arranged betweenadjacent PTFE yarns, to obtain a woven fabric. The resulting wovenfabric was pressure-bonded by a roll to obtain a woven fabric having athickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin B of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having a primary particle sizeof 1 μm was added to a 5% by mass ethanol solution of the acid-typeresin of the resin B and dispersed to prepare a suspension, and thesuspension was sprayed onto both the surfaces of the above compositemembrane by a suspension spray method to form coatings of zirconiumoxide on the surfaces of the composite membrane to obtain an ionexchange membrane A. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.5 mg/cm². Here, the average particlesize was measured by a particle size analyzer (manufactured by SHIMADZUCORPORATION, “SALD(R) 2200”).

As the electrode, a cathode and an anode below were used.

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 22 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.95 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching. The opening ratio was 44%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA. METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced was 9 μm. Thethickness of the catalytic layer containing ruthenium oxide and ceriumoxide, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm. The coating was formed also on the surface notroughened.

A titanium nonwoven fabric having a gauge thickness of 100 μm, atitanium fiber diameter of about 20 μm, a basis weight of 100 g/m², andan opening ratio of 78% was used as the substrate for electrode foranode electrolysis.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (E=1) (INOAC CORPORATION, E-4088,thickness 10 mm) around a chloride (PVC) cylinder was always in contactwith the coating liquid. A coating roll around which the same EPDM hadbeen wound was placed at the upper portion thereof, and PVC roller wasfurther placed thereabove. The coating liquid was applied by allowingthe substrate for electrode to pass between the second coating roll andthe PVC roller at the uppermost portion (roll coating method). After theabove coating liquid was applied onto the titanium porous foil, dryingat 60° C. for 10 minutes, and baking at 475° C. for 10 minutes wereperformed. A series of these coating, drying, preliminary baking, andbaking operations was repeatedly performed, and then baking at 520° C.was performed for an hour.

Example 5-1 (Example of Use of Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four cathodes having a size of 0.3 m in length and 2.4 m in width wereprovided in accordance with the method mentioned above.

After the ion exchange membrane was immersed in a 2% sodium bicarbonatesolution for a whole day and night, the cathodes were arranged withoutany gap on the carboxylic acid layer side of the ion exchange membraneto produce a laminate of the cathodes and the ion exchange membrane (seeFIG. 100). When the cathodes were placed on the membrane, the contactwith the sodium bicarbonate aqueous solution caused surface tension tofunction, and the cathodes and the membrane were integrated as if theystick together. No pressure was applied for such integration. Thetemperature at the integration was 23° C. The resulting laminate waswound around a polyvinyl chloride (PVC) pipe having an outer diameter of76 mm and a length of 1.7 m as shown in FIG. 101 to produce a woundbody. The wound body was in a cylindrical form having an outer diameterof 84 mm and a length of 1.7 m, and it was possible to downsize thelaminate.

Next, in an existing large electrolyzer (electrolyzer having a structuresimilar to those shown in FIGS. 93 and 94), a fixed state of theadjacent electrolytic cells and the ion exchange membrane by means of apress device was released, and the existing membrane was removed out toprovide a gap between the electrolytic cells. Thereafter, the wound bodywas conveyed onto the large electrolyzer. On the large electrolyzer,while the PVC pipe was upright, the wound state was released so as topull out the wound laminate. At this time, the laminate was maintainedsubstantially vertically to the ground, but the cathode did not comeoff. Then, after the laminate was inserted between the electrolyticcells, the electrolytic cells were moved to sandwich the laminatetherebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 5-2 (Example of Use of Anode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four anodes having a size of 0.3 m in length and 2.4 m in width wereprovided in accordance with the method mentioned above.

After the ion exchange membrane was immersed in a 2% sodium bicarbonatesolution for a whole day and night, the anodes were arranged without anygap on the sulfonic acid layer side in the same manner as in Example 5-1to produce a laminate of the anodes and the ion exchange membrane. Whenthe anodes were placed on the membrane, the contact with the sodiumbicarbonate aqueous solution caused surface tension to function, and theanodes and the membrane were integrated as if they stick together. Nopressure was applied for such integration. The temperature at theintegration was 23° C. The resulting laminate was wound around apolyvinyl chloride (PVC) pipe having an outer diameter of 76 μm and alength of 1.7 m to produce a wound body in the same manner as in Example5-1. The wound body was in a cylindrical form having an outer diameterof 86 mm and a length of 1.7 m, and it was possible to downsize thelaminate.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 5-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode did not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 5-3 (Example of Use of Anode/Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four anodes and four cathodes each having a size of 0.3 m in length and2.4 m in width were provided in accordance with the method mentionedabove.

After the ion exchange membrane was immersed in a 2% sodium bicarbonatesolution for a whole day and night, the cathodes were arranged on thecarboxylic acid layer side and the anodes were arranged on the sulfonicacid layer side without any gap in the same manner as in Example 5-1 toproduce a laminate of the cathodes, the anodes, and the ion exchangemembrane. When the cathodes and the anodes were placed on the membrane,the contact with the sodium bicarbonate aqueous solution caused surfacetension to function, and the cathodes, the anodes, and the membrane wereintegrated as if they stick together. No pressure was applied for suchintegration. The temperature at the integration was 23° C. The resultinglaminate was wound around a polyvinyl chloride (PVC) pipe having anouter diameter of 76 mm and a length of 1.7 m to produce a wound body inthe same manner as in Example 5-1. The wound body was in a cylindricalform having an outer diameter of 88 mm and a length of 1.7 m, and it waspossible to downsize the laminate.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 5-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe was,upright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode lid not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easer than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 5-4 (Example of Use of Cathodes)

A wound body was prod iced in advance as follows. First, four cathodeshaving a size of 0.3 m in length and 2.4 m in width were provided inaccordance with the method mentioned above. The four cathodes werearranged without any gap so as to achieve a size of 1.2 m in length and2.4 in width. Adjacent cathodes were tied together and fixed such thatthe cathodes were not separated by threading a PTFE string throughopenings of each cathode (not shown) as shown in FIG. 102. In theoperation, no pressure was applied, and the temperature was 23° C. Thesecathodes were wound around a polyvinyl chloride (PVC) pipe having anouter diameter of 76 mm and a length of 1.7 m to produce a wound body inthe same manner as in Example 5-1. The wound body was in a cylindricalform having an outer diameter of 78 mm and a length of 1.7 m, and it waspossible to downsize the laminate.

Next in an existing large electrolyzer (electrolyzer similar to that inExample 5-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundcathodes. At this time, the cathodes were maintained substantiallyvertically to the ground, but the cathodes did not come off. Then, afterthe cathodes were inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace cathodes easier than in conventional ones. Itwas judged that renewing of the cathodes can be completed in severaltens of minutes per one cell when a cathode wound body is provided inadvance during the electrolytic operation.

Example 5-5 (Example of Use of Anodes)

A wound body was produced in advance as follows.

First, four anodes having a size of 0.3 m in length and 2.4 m in widthwere provided in accordance with the method mentioned above. The fouranodes were arranged without any gap so as to achieve a size of 1.2 m inlength and 2.4 in width. Adjacent anodes were tied together with a PTFEstring and fixed such that the anodes were not separated, in the samemanner as in Example 5-4. In the operation, no pressure was applied, andthe temperature was 23° C. These anodes were wound around a polyvinylchloride (PVC) pipe having an outer diameter of 76 mm and a length of1.7 m to produce a wound body in the same manner as in Example 5-1. Thewound body was in a cylindrical form having an outer diameter of 81 mmand a length of 1.7 m, and it was possible to downsize the laminate.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 5-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundanodes. At this time, the anodes were maintained substantiallyvertically to the ground, but the anodes did not come off. Then, afterthe anodes were inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace anodes easier than in conventional ones. Itwas judged that renewing of the anodes can be completed, in several tensof minutes per one cell when an anode wound body is provided in advanceduring the electrolytic operation.

Comparative Example 5-1 (Conventional Renewing of Electrode)

In an existing large electrolyzer (electrolyzer similar to that inExample 5-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the electrolytic cells were hoisted outfrom the large electrolyzer with a hoist. The electrolytic cells removedwere conveyed to a plant where welding was available.

After the anode fixed by welding on the rib of the electrolytic cell wasstripped off, burrs or the like at the portion from which the anode wasstripped off with a grinder and so on to smooth the portion. The cathodewas stripped off by removing the portion fixed by folding the portioninto the collector.

Thereafter, a new anode was placed on the rib of the anode chamber, andthe new anode was fixed to the electrolytic cell by spot welding.Similarly in the case of the cathode, a new cathode was placed on thecathode side and fixed by folding the cathode into the collector.

The renewed electrolytic cell was conveyed to the position of the largeelectrolyzer, and the electrolytic cell was returned is the electrolyzerusing a hoist.

The period required from the release of the fixed state of theelectrolytic cell and the ion exchange membrane to the refixing of theelectrolytic cell was one day or more.

<Verification of Sixth Embodiment>

As will be described below, Experiment Examples according to the sixthembodiment (in the section of <Verification of sixth embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the sixth embodiment (in the section of <Verificationof sixth embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 105 and 106 asappropriate.

As the membrane, an ion exchange membrane b produced as described belowwas used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTE were used (hereinafter referred to as PTFEyarns). As the sacrifice yarns, yarns obtained by twisting six 35 denierfilaments of polyethylene terephthalate (PET) 200 times/m were used(hereinafter referred to as PET yarns). First, in each of the TD and theMD, the PTFE yarns and the sacrifice yarns were plain-woven with 24 PTFEyarns/inch so that two sacrifice yarns were arranged between adjacentPTFE yarns, to obtain a woven fabric. The resulting woven fabric waspressure-bonded by a roll to obtain a woven fabric having a thickness of70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/g, and a resin B of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having a primary particle sizeof 1 μm was added to a 5% by mass ethanol solution of the acid-typeresin of the resin B and dispersed to prepare a suspension, and thesuspension was sprayed onto both the surfaces of the above compositemembrane by a suspension spray method to form coatings of zirconiumoxide on the surfaces of the composite membrane to obtain an ionexchange membrane A. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.5 mg/cm². Here, the average particlesize was measured by a particle size analyzer (manufactured by SHIMADZUCORPORATION, “SALD(R) 2200”).

As the electrode, a cathode and an anode below were used.

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 22 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.95 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching. The opening ratio was 44%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium nitrate solution having aruthenium concentration of 100 g/L (FURUYA METAL Co., Ltd.) and ceriumnitrate (KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molarratio between the ruthenium element and the cerium element was 1:0.25.This mixed solution was sufficiently stirred and used as a cathodecoating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced was 29 μm. Thethickness of the catalytic layer containing ruthenium oxide and ceriumoxide, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness or theelectrode, was 7 μm. The coating was formed also on the surface notroughened.

A titanium nonwoven fabric having a gauge thickness of 100 μm, atitanium fiber diameter of about 20 μm, a basis weight of 100 μm², andan opening ratio of 78% was used as the substrate for electrode foranode electrolysis.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roil formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).After the above coating liquid was applied onto the titanium porousfoil, drying at 60° C. for 10 minutes, and baking at 475° C. for 10minutes were performed. A series of these coating, drying, preliminarybaking, and baking operations was repeatedly performed, and then bakingat 520° C. was performed for an hour.

Example 6-1 (Example of Use of Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane b having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four cathodes having a size of 0.3 m in length and 2.4 m in width wereprovided in accordance with the method mentioned above.

After the ion exchange membrane b was immersed in a 2% sodiumbicarbonate solution for a whole day and night, the cathodes werearranged without any gap on the carboxylic acid layer side of the ionexchange membrane to produce a laminate of the cathodes and the ionexchange membrane b. When the cathodes were placed on the membrane, thecontact with the sodium bicarbonate aqueous solution caused surfacetension to function, and the cathodes and the membrane were integratedas if they stick together. No pressure was applied for such integration.The temperature at the integration was 23° C. This laminate was woundaround a polyvinyl chloride (PVC) pipe having an outer diameter of 76 mmand a length of 1.7 m to produce a wound body. In order to melt the ionexchange membrane b, a temperature of 200° C. or more is required. Inthe present example, the ion exchange membrane did not melt duringintegration.

Next, in an existing large electrolyzer (electrolyzer having a structuresimilar to those shown in FIGS. 105 and 106), a fixed state of theadjacent electrolytic cells and the ion exchange membrane by means of apress device was released, and the existing membrane was removed out toprovide a gap between the electrolytic cells. Thereafter, the wound bodywas conveyed onto the large electrolyzer. On the large electrolyzer,while the PVC pipe was upright, the wound state was released so as topull out the wound laminate. At this time, the laminate was maintainedsubstantially vertically to the ground, but the cathode did not comeoff. Then, after the laminate was inserted between the electrolyticcells, the electrolytic cells were moved to sandwich the laminatetherebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell.

Example 6-2 (Example of Use of Anode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane b having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four anodes having a size of 0.3 m in length and 2.4 m in width wereprovided in accordance with the method mentioned above.

After the ion exchange membrane b was immersed in a 2% sodiumbicarbonate solution for a whole day and night, the anodes were arrangedwithout any gap on the sulfonic acid layer side of the ion exchangemembrane to produce a laminate of the anodes and the ion exchangemembrane. When the anodes were placed on the membrane, the contact withthe sodium bicarbonate aqueous solution caused surface tension tofunction, and the anodes and the membrane were integrated as if theystick together. No pressure was applied for such integration. Thetemperature at the integration was 23° C. This laminate was wound arounda polyvinyl chloride (PVC) pipe having an outer diameter of 76 mm and alength of 1.7 m to produce a wound body.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 6-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode did not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell.

Example 6-3 (Example of Use of Anode/Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane b having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four anodes and four cathodes each having a size of 0.3 m in length and2.4 m in width were provided in accordance with the method mentionedabove.

After the ion exchange membrane b was immersed in a 2% sodiumbicarbonate solution for a whole day and night, the cathodes werearranged on the carboxylic acid layer side of the ion exchange membraneand the anodes were arranged on the sulfonic acid layer side of the ionexchange membrane without any gap to produce a laminate of the cathodes,the anodes, and the ion exchange membrane b. When the cathodes and theanodes were placed on the membrane, the contact with the sodiumbicarbonate aqueous solution caused surface tension to function, and thecathodes, the anodes, and the membrane were integrated as if they sticktogether. No pressure was applied for such integration. The temperatureat the integration was 23° C. This laminate was wound around a polyvinylchloride (PVC) pipe having an outer diameter of 76 mm and a length of1.7 m to produce a wound body.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 6-1) a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode did not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell.

Comparative Example 6-1

A membrane electrode laminate was produced by thermally compressing anelectrode onto a membrane as follows, with reference to Examples ofJapanese Patent Laid-Open No. 58-48686.

A nickel expanded metal having a gauge thickness of 100 μm and anopening ratio of 33% was used as the substrate for electrode for cathodeelectrolysis to perform electrode coating in the same manner as inExample 6-1. The electrode had a size of 200 mm×200 mm, and the numberof the electrodes was 72. Thereafter, one surface of each electrode wassubjected to an inactivation treatment in the following procedure.Polyimide adhesive tape (Chukoh Chemical Industries, Ltd.) was attachedto one surface of the electrodes. A PTFE dispersion (Dupont-MitsuiFluorochemicals Co., Ltd., 31-JR (trade name)) was applied onto theother surface and dried in a muffle furnace at 120° C. for 10 minutes.The polyimide tape was peeled off, and a sintering treatment wasperformed in a muffle furnace set at 380° C. for 10 minutes. Thisoperation was repeated twice to inactivate the one surface of theelectrodes.

Produced was a membrane formed by two layers of a perfluorocarbonpolymer of which terminal functional group is “—COOCH₃” (C polymer) anda perfluorocarbon polymer of which terminal group is “—SO₂F” (Spolymer). The thickness of the C polymer layer was 3 mils, and thethickness of the S polymer layer was 4 mils. This two-layer membrane wassubjected to a saponification treatment to thereby introduce ionexchange groups to the terminals of the polymer by hydrolysis. The Cpolymer terminals were hydrolyzed into carboxylic acid groups and the Spolymer terminals into sulfo groups. The ion exchange capacity as thesulfonic acid group was 1.0 meq/g, and the ion exchange capacity as thecarboxylic acid group was 0.9 meg/g. The size of the resulting ionexchange membrane was similar to that in Example 6-1.

The inactivated electrode surface of the above electrode was oppositelydisposed to and thermally pressed (thermally compressed) onto thesurface having carboxylic acid groups as the ion exchange groups tointegrate the ion exchange membrane and the electrodes. That is, under atemperature at which the ion exchange membrane melted, the 12 electrodesof 200 mm square were integrated onto one ion exchange membrane having asize of 1500 mm in length and 2500 mm in width. The one surface of eachelectrode was exposed even after the thermal compression, and theelectrodes passed through no portion of the membrane.

For the large size of 1500 mm×2500 mm, a period of one day or more wasrequired for the process of integrating the ion exchange membrane andthe electrodes via thermal compression. That is, it was judged thatComparative Example 6-1 required a longer period for renewing of theelectrode and replacement of the membrane than in Examples.

<Verification of Seventh Embodiment>

As will be described below, Experiment Examples according to the seventhembodiment (in the section of <Verification of seventh embodiment>hereinbelow, simply referred to as “Examples”) and Experiment Examplesnot according to the seventh embodiment (in the section of <Verificationof seventh embodiment> hereinbelow, simply referred to as “ComparativeExamples”) were provided, and evaluated by the following method. Thedetails will be described with reference to FIGS. 114 and 115 asappropriate.

As the membrane, an ion exchange membrane produced as described belowwas used.

As reinforcement core materials, 90 denier monofilaments made ofpolytetrafluoroethylene (PTFE) were used (hereinafter referred to asPTFE yarns). As the sacrifice yarns, yarns obtained by twisting six 35denier filaments of polyethylene terephthalate (PET) 200 times/m wereused (hereinafter referred to as PET yarns). First, in each of the TDand the MD, the PTFE yarns and the sacrifice yarns were plain-woven with24 PTFE yarns/inch so that two sacrifice yarns were arranged betweenadjacent PTFE yarns, to obtain a woven fabric. The resulting wovenfabric was pressure-bonded by a roll to obtain a woven fabric having athickness of 70 μm.

Next, a resin A of a dry resin that was a copolymer of CF₂═CF₂ andCF₂═CFOCF₂CF(CF₃)OCF₂CF₂COOCH₃ and had an ion exchange capacity of 0.85mg equivalent/q, and a resin B of a dry resin that was a copolymer ofCF₂═CF₂ and CF₂═CFOCF₂CF(CF₃)OCF₂CF₂SO₂F and had an ion exchangecapacity of 1.03 mg equivalent/g were provided.

Using these resins A and B, a two-layer film X in which the thickness ofa resin A layer was 15 μm and the thickness of a resin B layer was 104μm was obtained by a coextrusion T die method.

Subsequently, release paper (embossed in a conical shape having a heightof 50 μm), a reinforcing material, and the film X were laminated in thisorder on a hot plate having a heat source and a vacuum source inside andhaving micropores on its surface, heated and depressurized under theconditions of a hot plate surface temperature of 223° C. and a degree ofreduced pressure of 0.067 MPa for 2 minutes, and then the release paperwas removed to obtain a composite membrane.

The resulting composite membrane was immersed in an aqueous solution at80° C. comprising 30% by mass of dimethyl sulfoxide (DMSO) and 15% bymass of potassium hydroxide (KOH) for 20 minutes for saponification.Then, the composite membrane was immersed in an aqueous solution at 50°C. comprising 0.5 N sodium hydroxide (NaOH) for an hour to replace thecounterion of the ion exchange group by Na, and then washed with water.Then, the membrane was dried at 60° C.

Further, 20% by mass of zirconium oxide having a primary particle sizeof 1 μm was added to a 5% by mass ethanol solution of the acid-typeresin of the resin B and dispersed to prepare a suspension, and thesuspension was sprayed onto both the surfaces of the above compositemembrane by a suspension spray method to form coatings of zirconiumoxide on the surfaces of the composite membrane to obtain an ionexchange membrane A. The coating density of zirconium oxide measured byfluorescent X-ray measurement was 0.5 mg/cm². Here, the average particlesize was measured by a particle size analyzer (manufactured by SHIMADZUCORPORATION, “SALD(R) 2200”).

As the electrode, a cathode and an anode below were used.

As a substrate for electrode for cathode electrolysis, an electrolyticnickel foil having a gauge thickness of 22 μm was provided. One surfaceof this nickel foil was subjected to a roughening treatment by means ofelectrolytic nickel plating. The arithmetic average roughness Ra of theroughened surface was 0.95 μm. The measurement of the surface roughnesswas performed under the same conditions as for the surface roughnessmeasurement of the nickel plate subjected to the blast treatment.

A porous foil was formed by perforating this nickel foil with circularholes by punching. The opening ratio was 44%.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure ruthenium nitrate solution having a rutheniumconcentration of 100 g/L (FURUYA METAL Co., Ltd.) and cerium nitrate(KISHIDA CHEMICAL Co., Ltd.) were mixed such that the molar ratiobetween the ruthenium element and the cerium element was 1:0.25. Thismixed solution was sufficiently stirred and used as a cathode coatingliquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roll around which the sameEPDM had been wound was placed at the upper portion thereof, and PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).Then, after drying at 50° C. for 10 minutes, preliminary baking at 150°C. for 3 minutes, and baking at 350° C. for 10 minutes were performed. Aseries of these coating, drying, preliminary baking, and bakingoperations was repeated until a predetermined amount of coating wasachieved. The thickness of the electrode produced was 29 μm. Thethickness of the catalytic layer containing ruthenium oxide and ceriumoxide, which was determined by subtracting the thickness of thesubstrate for electrode for electrolysis from the thickness of theelectrode, was 7 μm. The coating was formed also on the surface notroughened.

A titanium nonwoven fabric having a gauge thickness of 100 μm, atitanium fiber diameter of about 20 μm, a basis weight of 100 g/m², andan opening ratio of 78% was used as the substrate for electrode foranode electrolysis.

A coating liquid for use in forming an electrode catalyst was preparedby the following procedure. A ruthenium chloride solution having aruthenium concentration of 100 g/L (Tanaka Kikinzoku Kogyo K.K.),iridium chloride having an iridium concentration of 100 g/L (TanakaKikinzoku Kogyo K.K.), and titanium tetrachloride (Wako Pure ChemicalIndustries, Ltd.) were mixed such that the molar ratio among theruthenium element, the iridium element, and the titanium element was0.25:0.25:0.5. This mixed solution was sufficiently stirred and used asan anode coating liquid.

A vat containing the above coating liquid was placed at the lowermostportion of a roll coating apparatus. The vat was placed such that acoating roll formed by winding rubber made of closed-cell type foamedethylene-propylene-diene rubber (EPDM) (INOAC CORPORATION, E-4088,thickness 10 mm) around a polyvinyl chloride (PVC) cylinder was alwaysin contact with the coating liquid. A coating roil around which the sameEPDM had been wound was placed at the upper portion thereof, and a PVCroller was further placed thereabove. The coating liquid was applied byallowing the substrate for electrode to pass between the second coatingroll and the PVC roller at the uppermost portion (roll coating method).After the above coating liquid was applied onto the titanium porousfoil, drying at 60° C. for 10 minutes, and baking at 475° C. for 10minutes were performed. A series of these coating, drying, preliminarybaking, and baking operations was repeatedly performed, and then bakingat 520° C. was performed for an hour.

Example 7-1 (Example of Use of Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four cathodes having a size of 0.3 m in length and 2.4 m in width wereprovided in accordance with the method mentioned above.

After the ion exchange membrane was immersed in a 2% sodium bicarbonatesolution for a whole day and night, the cathodes were arranged withoutany gap on the carboxylic acid layer side of the ion exchange membraneto produce a laminate of the cathodes and the ion exchange membrane.When the cathodes were placed on the membrane, the contact with thesodium bicarbonate aqueous solution caused surface tension to function,and the cathodes and the membrane were integrated as if they sticktogether. No pressure was applied for such integration. The temperatureat the integration was 23° C. This laminate was wound around a polyvinylchloride (PVC) pipe having an outer diameter of 76 mm and a length of1.7 m to produce a wound body.

Next, in an existing large electrolyzer (electrolyzer having a structuresimilar to those shown in FIGS. 114 and 115), a fixed state of theadjacent electrolytic cells and the ion exchange membrane by means of apress device was released, and the existing membrane was removed out toprovide a gap between the electrolytic cells. Thereafter, the wound bodywas conveyed onto the large electrolyzer. On the large electrolyzer,while the PVC pipe was upright, the wound state was released so as topull out the wound laminate. At this time, the laminate was maintainedsubstantially vertically to the ground, but the cathode did not comeoff. Then, after the laminate was inserted between the electrolytic cellthe electrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 7-2 (Example of Use of Anode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1 m in length and 2.5 m in width was providedin accordance with the method mentioned above. Additionally, four anodeshaving a size of 0.3 m in length and 2.4 m in width were provided inaccordance with the method mentioned above.

After the ion exchange membrane was immersed In a 2% sodium bicarbonatesolution for a whole day and night, the anodes were arranged without anygap on the sulfonic acid layer side of the ion exchange membrane toproduce a laminate of the anodes and the ion exchange membrane. When theanodes were placed on the membrane, the contact with the sodiumbicarbonate aqueous solution caused surface tension to function, and theanodes and the membrane were integrated as if they stick together. Nopressure was applied for such integration. The temperature at theintegration was 23° C. This laminate was wound around a polyvinylchloride (PVC) pipe having an outer diameter of 76 mm and a length of1.7 m to produce a wound body.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 7-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a cap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode did not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 7-3 (Example of Use of Anode/Cathode-Membrane Laminate)

A wound body was produced in advance as follows. First, an ion exchangemembrane having a size of 1.5 m in length and 2.5 m in width wasprovided in accordance with the method mentioned above. Additionally,four anodes and four cathodes each having a size of 0.3 m in length and2.4 m in width were provided in accordance with the method mentionedabove.

After the ion exchange membrane was immersed in a 2% sodium bicarbonatesolution for a whole day and night, the cathodes were arranged on thecarboxylic acid layer side of the ion exchange membrane and the anodeswere arranged on the sulfonic acid layer side of the ion exchangemembrane without any gap to produce a laminate of the cathodes, theanodes, and the ion exchange membrane. When the cathodes and the anodeswere placed on the membrane, the contact with the sodium bicarbonateaqueous solution caused surface tension to function, and the cathodes,the anodes, and the membrane were integrated as if they stick together.No pressure was applied for such integration. The temperature at theintegration was 23° C. This laminate was wound around a polyvinylchloride (PVC) pipe having an outer diameter of 76 mm and a length of1.7 m to produce a wound body.

Next in an existing large electrolyzer (electrolyzer similar to that inExample 7-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundlaminate. At this time, the laminate was maintained substantiallyvertically to the ground, but the anode did not come off. Then, afterthe laminate was inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the laminate therebetween.

It was possible to replace the electrode and the membrane easier than inconventional ones. It was judged that renewing of the electrode andreplace of the membrane can be completed in several tens of minutes perone cell when a laminate wound body is provided in advance during theelectrolytic operation.

Example 7-4 (Example of Use of Cathodes)

A wound body was produced in advance as follows. First, four cathodeshaving a size of 0.3 m in length and 2.4 m in width were provided inaccordance with the method mentioned above. The four cathodes werearranged without any gap so as to achieve a size of 1.2 m in length and2.4 m in width. Adjacent cathodes were tied together with a PTFE stringand fixed such that the cathodes were not separated. In the operation,no pressure was applied, and the temperature was 23° C. These cathodeswere wound around a polyvinyl chloride (PVC) pipe having an outerdiameter having an of 76 mm and a length of 1.7 m to produce a woundbody.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 7-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundcathodes. At this time, the cathodes were maintained substantiallyvertically to the ground, but the cathodes did not come off. Then, afterthe cathodes were inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the cathodes therebetween.

It was possible to replace cathodes easier than in conventional ones. Itwas judged that renewing of the cathodes can be completed in severaltens of minutes per one cell when a cathode wound body is provided inadvance during the electrolytic operation.

Example 7-5 (Example of Use of Anodes)

A wound body was produced in advance as follows. First, four anodeshaving a size of 0.3 m in length and 2.4 m in width were provided inaccordance with the method mentioned above. The four anodes werearranged without any gap so as to achieve a size of 1.2 m in length and2.4 m in width. Adjacent anodes were tied together with a PTFE stringand fixed such that the anodes were not separated. In the operation, nopressure was applied, and the temperature was 23° C. These anodes werewound around a polyvinyl chloride (PVC) pipe having an outer diameter of76 mm and a length of 1.7 m to produce a wound body.

Next, in an existing large electrolyzer (electrolyzer similar to that inExample 7-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the wound body was conveyed onto thelarge electrolyzer. On the large electrolyzer, while the PVC pipe wasupright, the wound state was released so as to pull out the woundanodes. At this time, the anodes were maintained substantiallyvertically to the ground, but the anodes did not come off. Then, afterthe anodes were inserted between the electrolytic cells, theelectrolytic cells were moved to sandwich the anodes therebetween.

It was possible to replace anodes easier than in conventional ones. Itwas judged that renewing of the anodes can be completed in several tensof minutes per one cell when an anode wound body is provided in advanceduring the electrolytic operation.

Comparative Example 7-1 (Conventional Renewing of Electrode)

In an existing large electrolyzer (electrolyzer similar to that inExample 7-1), a fixed state of the adjacent electrolytic cells and theion exchange membrane by means of a press device was released, and theexisting membrane was removed out to provide a gap between theelectrolytic cells. Thereafter, the electrolytic cells were hoisted outfrom the large electrolyzer with a hoist. The electrolytic cells removedwere conveyed to a plant where welding was available.

After the anode fixed by welding on the rib of the electrolytic cell wasstripped off, burrs or the like at the portion from which the anode wasstripped off with a grinder to smooth the portion. The cathode wasstripped off by removing the portion fixed by folding the portion intothe collector.

Thereafter, a new anode was placed on the rib of the anode chamber, andthe new anode was fixed to the electrolytic cell by spot welding.Similarly in the case of the cathode, a new cathode was placed on thecathode side and fixed by folding the cathode into the collector.

The renewed electrolytic cell was conveyed to the position of the largeelectrolyzer, and the electrolytic cell was returned in the electrolyzerusing a hoist.

The period required from the release of the fixed state of theelectrolytic cell and the ion exchange membrane to the refixing of theelectrolytic cell was one day or more.

The present application is based on Japanese Patent Applications filedon Mar. 22, 2017 (Japanese Patent Applications No. 2017-056524 and No.2017-056525) and Japanese Patent Applications filed on Mar. 20, 2018(Japanese Patent Applications No. 2018-053217, No. 2018-053146, No.2018-053144, No. 2018-053231, No. 2018-053145, No. 2018-053149, and No.2018-053139), the contents of which are herein incorporated byreference.

REFERENCE SIGNS LIST <Figures for First Embodiment> Reference Signs Listfor FIG. 1

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 2 to 4

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

Reference Signs List for FIGS. 5 to 9

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wail

40 . . . cathode structure for electrolysis

Reference Signs List for FIG. 10

1 . . . pinch jig (SUS)

2 . . . electrode

3 . . . membrane

4 . . . nickel plate (blasted with alumina of grain-size number 320)

100 . . . front face

200 . . . side face

Reference Signs List for FIGS. 11 to 13

1 . . . membrane

2 a . . . polyethylene pipe having an outer diameter of 280 mm

2 b . . . polyethylene pipe having an outer diameter of 145 mm

3 . . . delaminated portion

4 . . . close contact portion

5 . . . electrode

Reference Signs List for FIG. 14

1 . . . polyvinyl chloride (PVC) pipe

2 . . . ion exchange membrane

3 . . . electrode

4 . . . surface plate

Reference Signs List for FIG. 15

1 . . . surface plate

2 . . . deformed electrode

10 . . . jig for fixing electrode

20 . . . direction in which a force is applied

Reference Signs List for FIGS. 16 to 21

1 . . . 110 mm nickel line

2 . . . 950 mm nickel line

3 . . . frame

<Figures for Second Embodiment> Reference Signs List for FIG. 22

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 23 to 25

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

Reference Signs List for FIGS. 26 to 30

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wall

40 . . . cathode structure for electrolysis

Reference Signs List for FIG. 31

1 . . . pinch jig (SUS)

2 . . . electrode

3 . . . membrane

4 . . . nickel plate (blasted with alumina of grain-size number 320)

100 . . . front face

200 . . . side face

Reference Signs List for FIGS. 32 to 34

1 . . . membrane

2 a . . . polyethylene pipe having an outer diameter of 280 mm

2 b . . . polyethylene pipe having an outer diameter of 145 mm

3 . . . delaminated portion

4 . . . close contact portion

5 . . . electrode

Reference Signs List for FIG. 35

1 . . . polyvinyl chloride (PVC) pipe

2 . . . ion exchange membrane

3 . . . electrode

4 . . . surface plate

Reference Signs List for FIG. 36

1 . . . surface plate

2 . . . deformed electrode

10 . . . jig for fixing electrode

20 . . . direction in which a force is applied

Reference Signs List for FIGS. 37 to 42

1 . . . 110 mm nickel line

2 . . . 950 mm nickel line

3 . . . frame

<Figures for Third Embodiment> Reference Signs List for FIG. 43

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 44 to 46

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole 504

Reference Signs List for FIGS. 47 to 51

1 . . . laminate

2 . . . electrode for electrolysis

2 a . . . inner surface of electrode for electrolysis

2 b . . . outer surface of electrode for electrolysis

3 . . . membrane

3 a . . . inner surface of membrane

3 b . . . outer surface of membrane

7 . . . fixing member

Reference Signs List for FIGS. 52 to 56

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wail

40 . . . cathode structure for electrolysis

<Figures for Fourth Embodiment> Reference Signs List for FIGS. 63 to 67

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wall

40 . . . cathode structure for electrolysis

Reference Signs List for FIG. 68

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 69 to 71

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

Reference Signs List for FIGS. 72 to 78

1 . . . laminate

2 . . . electrode for electrolysis

2 a . . . inner surface of electrode for electrolysis

2 b . . . outer surface of electrode for electrolysis

3 . . . membrane

3 a . . . inner surface of membrane

3 b . . . outer surface of membrane

7 . . . fixing member

A . . . gasket

B . . . membrane

C . . . electrode for electrolysis

A1 . . . outermost perimeter of gasket

B1 . . . outermost perimeter of membrane

C1 . . . outermost perimeter of electrode for electrolysis

Reference Signs List for FIG. 79

1 . . . pinch jig (SUS)

2 . . . electrode

3 . . . membrane

4 . . . nickel plate (blasted with alumina of grain-size number 320)

100 . . . front face

200 . . . side face

Reference Signs List for FIGS. 80 to 82

1 . . . membrane

2 a . . . polyethylene pipe having an outer diameter of 280 mm

2 b . . . polyethylene pipe having an outer diameter of 145 mm

3 . . . delaminated portion

4 . . . close contact portion

5 . . . electrode

Reference Signs List for FIG. 84

1 . . . surface plate

2 . . . deformed electrode

10 . . . jig for fixing electrode

20 . . . direction in which a force is applied

Reference Signs List for FIGS. 85 to 90

1 . . . 110 mm nickel line

2 . . . 950 mm nickel line

3 . . . frame

<Figures for Fifth Embodiment> Reference Signs List for FIGS. 91 to 95

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wall

40 . . . cathode structure for electrolysis

Reference Signs List for FIG. 96

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 97 to 99

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

<Figures for Sixth Embodiment> Reference Signs List for FIGS. 103 to 107

1 . . . electrolytic cell

2 . . . ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wall

40 . . . cathode structure for electrolysis

Reference Signs List for FIG. 108

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 109 to 111

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

<Figures for Seventh Embodiment> Reference Signs List for FIGS. 112 to118

1 . . . electrolytic cell

2 . . . ion exchange membrane

2 a . . . new ion exchange membrane

4 . . . electrolyzer

5 . . . press device

6 . . . cathode terminal

7 . . . anode terminal

8 . . . electrolyzer frame

9 . . . laminate

10 . . . anode chamber

11 . . . anode

12 . . . anode gasket

13 . . . cathode gasket

18 . . . reverse current absorber

18 a . . . substrate

18 b . . . reverse current absorbing layer

19 . . . bottom of anode chamber

20 . . . cathode chamber

21 . . . cathode

22 . . . metal elastic body

23 . . . collector

24 . . . support

30 . . . partition wail

40 . . . cathode structure for electrolysis

100 . . . electrode for electrolysis

Reference Signs List for FIG. 119

10 . . . substrate for electrode for electrolysis

20 . . . first layer

30 . . . second layer

100 . . . electrode for electrolysis

Reference Signs List for FIGS. 120 to 122

1 . . . ion exchange membrane

2 . . . carboxylic acid layer

3 . . . sulfonic acid layer

4 . . . reinforcement core material

10 . . . membrane body

11 a, 11 b . . . coating layer

21, 22 . . . reinforcement core material

100 . . . electrolyzer

200 . . . anode

300 . . . cathode

52 . . . reinforcement yarn

504 a . . . sacrifice yarn

504 . . . continuous hole

1. An electrode for electrolysis having a mass per unit area of 48 mg/cm² or less and a force applied per unit mass·unit area of 0.08 N/mg·cm² or more.
 2. The electrode for electrolysis according to claim 1, wherein the electrode for electrolysis comprises a substrate for electrode for electrolysis and a catalytic layer, and the substrate for electrode for electrolysis has a thickness of 300 μm or less.
 3. The electrode for electrolysis according to claim 1 or 2, wherein a proportion measured by a method (3) below is 75% or more: [Method (3)] An ion exchange membrane (170 mm square), which is obtained by applying inorganic material particles and a binder to both surfaces of a membrane of a perfluorocarbon polymer into which an ion exchange group is introduced and a sample of electrode for electrolysis (130 mm square) are laminated in this order; and the laminate is placed on a curved surface of a polyethylene pipe (outer diameter: 145 mm) such that the sample of electrode for electrolysis in this laminate is positioned outside under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, the laminate and the pipe are sufficiently immersed in pure water, excess water deposited on a surface of the laminate and the pipe is removed, and one minute after this removal, then a proportion) of an area of a portion, in which the sample of electrode for electrolysis is in close contact with the membrane obtained by applying the inorganic material particles and the binder to both the surfaces of the membrane of the perfluorocarbon polymer into which the ion exchange group is introduced, is measured.
 4. The electrode for electrolysis according to claim 1 or 2, wherein the electrode for electrolysis has a porous structure and has an opening ratio of 5 to 90%.
 5. The electrode for electrolysis according to claim 1 or 2, wherein the electrode has a porous structure and has an opening ratio of 10 to 80%.
 6. The electrode for electrolysis according to claim 1 or 2, wherein the electrode for electrolysis has a thickness of 315 or less.
 7. The electrode for electrolysis according to claim 1 or 2, wherein a value obtained by measuring the electrode for electrolysis by a method (A) below is 40 mm or less: [Method (A)] Under conditions of a temperature of 23±2° C. and a relative humidity of 30±5%, a sample obtained by laminating the ion exchange membrane and the electrode for electrolysis is wound around and fixed onto a curved surface of a core material being made of polyvinyl chloride and having an outer diameter ϕ of 32 mm, and left to stand for 6 hours; thereafter, when the electrode for electrolysis is separated from the sample and placed on a flat plate, heights in a vertical direction at both edges of the electrode for electrolysis L₁ and L₂ are measured, and an average value thereof is used as a measurement value.
 8. The electrode for electrolysis according to claim 1 or 2, wherein a ventilation resistance is 24 kPa·s/m or less when the electrode for electrolysis has a size of 50 mm×50 mm, the ventilation resistance being measured under conditions of the temperature of 24° C., the relative humidity of 32%, a piston speed of 0.2 cm/s, and a ventilation volume of 0.4 cc/cm²/s.
 9. (canceled)
 10. A laminate comprising the electrode for electrolysis according to claim 1 or
 2. 11. A wound body comprising the electrode for electrolysis according to claim 1 or
 2. 12. A laminate comprising: an electrode for electrolysis, and a membrane or feed conductor in contact with the electrode for electrolysis, wherein a force applied per unit mass·unit area of the electrode for electrolysis on the membrane or feed conductor is less than 1.5 N/mg·cm².
 13. The laminate according to claim 12, wherein the force applied per unit mass·unit area of the electrode for electrolysis on the membrane or feed conductor is more than 0.005 N/mg·cm².
 14. The laminate according to claim 12 or 13, wherein the feed conductor is a wire mesh, a metal nonwoven fabric, a perforated metal, an expanded metal, or a foamed metal.
 15. The laminate according to claim 12 or 13, comprising, as at least one surface layer of the membrane, a layer comprising a mixture of hydrophilic oxide particles and a polymer into which ion exchange groups are introduced.
 16. The laminate according to claim 12 or 13, wherein a liquid is interposed between the electrode for electrolysis and the membrane or feed conductor. 17-60. (canceled) 